Activewear Tech Packs: How to Specify Stretch, Recovery, and Flatlock Stitching
Master activewear tech packs with detailed specs for stretch, recovery percentages, flatlock stitching, and labelling. The definitive guide for performance apparel.
Activewear Tech Packs: How to Specify Stretch, Recovery, and Flatlock Stitching
An activewear tech pack is a technical specification document that defines every material, measurement, and construction detail required to manufacture performance apparel. Unlike a tech pack for a basic t-shirt, it must specify exact fabric stretch percentages, recovery values, seam types (such as flatlock to ISO 607), and labelling decisions that affect both comfort and durability. Getting these specifications right is what separates leggings that hold their shape after 50 washes from ones that bag out after five.
Activewear is the most technically demanding category most emerging brands will ever produce. A poorly written tech pack here doesn't just cost you sample rounds—it costs you returns, reviews, and repeat customers. This guide walks through the three areas where founders most often under-specify: fabric stretch and recovery, flatlock seam construction, and labelling for skin-contact garments.
Why activewear tech packs are different
A standard apparel tech pack covers materials, measurements, construction, and trims. A performance apparel tech pack does all of that, plus it has to control for things the human body does at high intensity: stretch, sweat, friction, and repeated mechanical stress.
Factories cannot guess these things. If your tech pack just says "4-way stretch jersey" or "flatlock seams," you've handed the factory at least three different ways to interpret your design—and they'll pick the one that's easiest for them, not the one that performs best for your customer.
A complete activewear tech pack specifies:
Fabric composition with stretch and recovery percentages (not just "stretchy")
GSM (grams per square metre) and finish (peached, brushed, matte)
Seam construction by ISO code, with stitch type, SPI (stitches per inch), and thread weight
Bonded or taped seams where relevant (for compression or seamless aesthetics)
Labelling method: woven, heat-transfer, or printed directly to fabric
Care instructions matched to fibre content and finishes
If you're new to the document itself, our comprehensive tech pack guide covers the foundational structure. This article goes deeper into the activewear-specific layers.
Specifying fabric: why "4-way stretch" isn't enough
The single most common mistake on a gym wear tech pack is treating stretch as a binary feature. "4-way stretch" tells the factory the fabric moves in all directions. It tells them nothing about how much it moves or whether it returns to its original shape afterwards.
Stretch vs. recovery: the distinction that matters
Stretch is how far a fabric extends under tension. Recovery is how much of that extension it loses when the tension is released. A fabric can have excellent stretch and terrible recovery—that's the leggings-bagging-at-the-knees problem in a nutshell.
Performance fabrics should be specified with both values. For example:
Stretch: 80% widthwise / 60% lengthwise
Recovery: 95% widthwise / 92% lengthwise after 30 seconds
Recovery below roughly 90% is generally unacceptable for compression activewear. For everyday leggings or joggers, 85% is often workable. Below 80% and the garment will lose its shape within weeks.
The stretch and recovery test (ASTM D2594 / D3107)
This is the industry-standard test methodology your factory's lab can run on a swatch. The fabric is stretched to a fixed load (or a fixed extension), held, released, and measured again after a set rest period.
Specify on your tech pack:
Test method (e.g., ASTM D2594 for knits)
Required stretch % in both directions
Required recovery % after a specified rest period (typically 30 seconds and 60 minutes)
Number of cycles the fabric must endure before losing recovery (e.g., 5,000 cycles minimum)
Without these numbers, "performance fabric" is just marketing copy.
Composition guidance for activewear knits
Most activewear sits in one of these compositions:
Nylon/spandex (78/22 to 82/18) — high recovery, soft hand, ideal for compression
Polyester/spandex (87/13 to 90/10) — better moisture wicking, more affordable, slightly lower recovery
Poly/nylon/spandex tri-blends — engineered for specific performance attributes
Spandex content below 12% rarely delivers true compression. Above 22% and the fabric becomes expensive and harder to sew cleanly.
Flatlock stitching: the ISO 607 deep dive
Flatlock stitching is the seam construction standard for skin-contact performance apparel. It's not a single stitch—it's a family of stitches classified under ISO 4915 Stitch Class 600 (commonly referenced via the broader ISO 607 framework for flat seam construction).
Why flatlock exists
Conventional overlock seams (the kind on a basic t-shirt) leave a raised ridge on the inside of the garment. Under a sports bra strap, along the inner thigh of leggings, or under the arm of a running shirt, that ridge becomes a friction point. Friction plus sweat plus repeated movement equals chafing—the number-one source of activewear returns and bad reviews.
Flatlock stitches join two pieces of fabric edge-to-edge (rather than overlapping them) and create a flat, almost imperceptible seam on both sides of the garment. The result:
No raised ridge against the skin
Better stretch along the seam line (flatlock seams stretch with the fabric rather than restricting it)
Cleaner aesthetic, often used as a visible design feature
How to specify flatlock correctly
On your sportswear tech pack template, every seam should be called out with:
ISO stitch class (e.g., 607 for a 4-needle flatlock)
Needle count (3-needle vs. 4-needle—4-needle is wider, more durable, and standard for activewear)
SPI (stitches per inch) — typically 10–12 for flatlock
Thread type and weight — usually textured polyester (e.g., 150D textured poly for the looper, 75D for the needle)
Seam allowance — flatlock typically uses 6mm
Location callouts — exactly which seams use flatlock vs. coverstitch vs. bonded construction
When not to use flatlock
Flatlock isn't a universal answer. It's not appropriate for:
High-tension load-bearing seams like the gusset of leggings (use a chain stitch + coverstitch combo)
Waistbands (coverstitch or bonded elastic is stronger)
Bonded or seamless designs where adhesive tape replaces stitching entirely
A good tech pack maps each seam on the garment to the correct construction. Avoid the rookie move of writing "flatlock throughout" without thinking through load-bearing zones.
For a refresher on what goes wrong when tech packs lack this specificity, see our breakdown of common tech pack mistakes.
Labelling activewear: heat-transfer vs. woven
Labels are a small detail with an outsized effect on the wearer's experience. For activewear, this is where comfort and durability genuinely conflict—and your tech pack has to make a deliberate call.
Woven labels
Pros:
Durable—survive hundreds of wash cycles legibly
Premium hand-feel and look
Cheap at scale (a few cents each)
Cons:
Stiff edges can scratch and chafe against skin
Require a folded seam to attach, adding bulk
Itch factor is the #1 complaint in performance apparel reviews
Woven labels work for outerwear, jackets, or anywhere the label sits over a base layer. For next-to-skin activewear, they're often a poor choice.
Heat-transfer labels (HTL)
Pros:
No physical edges—nothing to scratch the skin
Lightweight and flexible, stretches with the fabric
Can be placed anywhere, including on technical fabrics
Ideal for compression wear, sports bras, and seamless garments
Cons:
Lower durability—edges can lift or crack after 30–50+ wash cycles if poorly applied
Application quality is highly factory-dependent
Slightly more expensive per unit
Printed labels (direct-to-garment)
A third option, increasingly common in premium activewear: screen-printed or DTG-printed labels applied directly to the inside of the garment. These are even softer than HTLs but require careful ink selection to survive performance-fabric care cycles.
How to specify on your tech pack
Don't just write "heat transfer label." Specify:
Label type (HTL, woven, printed)
Dimensions in mm
Placement (e.g., 50mm below centre back neck, inside)
Content (brand mark, size, fibre composition, country of origin, care symbols)
For HTLs: film type (matte vs. gloss), application temperature and pressure if known
Durability requirement (e.g., must remain legible after 50 wash cycles per care instructions)
Pulling it together: a working activewear tech pack checklist
If you're building or auditing a performance apparel specifications document, run through this checklist:
Fabric — composition, GSM, finish, stretch %, recovery %, test method
Trims — elastic type and stretch, drawcords, stoppers, eyelets, with all specifications
Construction map — every seam labelled with ISO stitch class, SPI, thread, and seam allowance
Bonded or taped seams — adhesive type, width, and placement if applicable
Labels — type, placement, content, durability spec
Measurements — graded points of measurement (POM) chart with tolerances
Care instructions — matched to fibre content and tested for performance retention
Colourway and print details — Pantone references, sublimation files if relevant
Packaging and folding spec — important for activewear's premium positioning
Activewear development is iterative. Expect 3–5 sample rounds before bulk production, especially for compression pieces. Building this level of detail into your tech pack upfront cuts the number of rounds dramatically.
Where Specter OS fits in
Compiling all of this in a spreadsheet works—until you're managing three colourways, two factories, and a fit revision on the back gusset of your leggings. That's where things fall apart.
Platforms like Specter OS centralise the entire activewear tech pack workflow: a pre-loaded CAD library for performance apparel, structured fields for stretch and recovery percentages, ISO stitch class callouts, and direct factory communication tied to each tech pack version. When your factory comments on a flatlock seam at the inner thigh, the conversation lives next to the spec—not lost in an email thread.
Specter OS offers a free tier built specifically for emerging brands navigating their first complex tech packs. If you're moving from t-shirts to performance wear, that transition is where having a single source of truth matters most.
You can explore the [case for using a fashion OS](/blog/why-fashion-brands-need-an-os
Activewear Tech Packs: How to Specify Stretch, Recovery, and Flatlock Stitching
Master activewear tech packs with detailed specs for stretch, recovery percentages, flatlock stitching, and labelling. The definitive guide for performance apparel.
Activewear Tech Packs: How to Specify Stretch, Recovery, and Flatlock Stitching
An activewear tech pack is a technical specification document that defines every material, measurement, and construction detail required to manufacture performance apparel. Unlike a tech pack for a basic t-shirt, it must specify exact fabric stretch percentages, recovery values, seam types (such as flatlock to ISO 607), and labelling decisions that affect both comfort and durability. Getting these specifications right is what separates leggings that hold their shape after 50 washes from ones that bag out after five.
Activewear is the most technically demanding category most emerging brands will ever produce. A poorly written tech pack here doesn't just cost you sample rounds—it costs you returns, reviews, and repeat customers. This guide walks through the three areas where founders most often under-specify: fabric stretch and recovery, flatlock seam construction, and labelling for skin-contact garments.
Why activewear tech packs are different
A standard apparel tech pack covers materials, measurements, construction, and trims. A performance apparel tech pack does all of that, plus it has to control for things the human body does at high intensity: stretch, sweat, friction, and repeated mechanical stress.
Factories cannot guess these things. If your tech pack just says "4-way stretch jersey" or "flatlock seams," you've handed the factory at least three different ways to interpret your design—and they'll pick the one that's easiest for them, not the one that performs best for your customer.
A complete activewear tech pack specifies:
Fabric composition with stretch and recovery percentages (not just "stretchy")
GSM (grams per square metre) and finish (peached, brushed, matte)
Seam construction by ISO code, with stitch type, SPI (stitches per inch), and thread weight
Bonded or taped seams where relevant (for compression or seamless aesthetics)
Labelling method: woven, heat-transfer, or printed directly to fabric
Care instructions matched to fibre content and finishes
If you're new to the document itself, our comprehensive tech pack guide covers the foundational structure. This article goes deeper into the activewear-specific layers.
Specifying fabric: why "4-way stretch" isn't enough
The single most common mistake on a gym wear tech pack is treating stretch as a binary feature. "4-way stretch" tells the factory the fabric moves in all directions. It tells them nothing about how much it moves or whether it returns to its original shape afterwards.
Stretch vs. recovery: the distinction that matters
Stretch is how far a fabric extends under tension. Recovery is how much of that extension it loses when the tension is released. A fabric can have excellent stretch and terrible recovery—that's the leggings-bagging-at-the-knees problem in a nutshell.
Performance fabrics should be specified with both values. For example:
Stretch: 80% widthwise / 60% lengthwise
Recovery: 95% widthwise / 92% lengthwise after 30 seconds
Recovery below roughly 90% is generally unacceptable for compression activewear. For everyday leggings or joggers, 85% is often workable. Below 80% and the garment will lose its shape within weeks.
The stretch and recovery test (ASTM D2594 / D3107)
This is the industry-standard test methodology your factory's lab can run on a swatch. The fabric is stretched to a fixed load (or a fixed extension), held, released, and measured again after a set rest period.
Specify on your tech pack:
Test method (e.g., ASTM D2594 for knits)
Required stretch % in both directions
Required recovery % after a specified rest period (typically 30 seconds and 60 minutes)
Number of cycles the fabric must endure before losing recovery (e.g., 5,000 cycles minimum)
Without these numbers, "performance fabric" is just marketing copy.
Composition guidance for activewear knits
Most activewear sits in one of these compositions:
Nylon/spandex (78/22 to 82/18) — high recovery, soft hand, ideal for compression
Polyester/spandex (87/13 to 90/10) — better moisture wicking, more affordable, slightly lower recovery
Poly/nylon/spandex tri-blends — engineered for specific performance attributes
Spandex content below 12% rarely delivers true compression. Above 22% and the fabric becomes expensive and harder to sew cleanly.
Flatlock stitching: the ISO 607 deep dive
Flatlock stitching is the seam construction standard for skin-contact performance apparel. It's not a single stitch—it's a family of stitches classified under ISO 4915 Stitch Class 600 (commonly referenced via the broader ISO 607 framework for flat seam construction).
Why flatlock exists
Conventional overlock seams (the kind on a basic t-shirt) leave a raised ridge on the inside of the garment. Under a sports bra strap, along the inner thigh of leggings, or under the arm of a running shirt, that ridge becomes a friction point. Friction plus sweat plus repeated movement equals chafing—the number-one source of activewear returns and bad reviews.
Flatlock stitches join two pieces of fabric edge-to-edge (rather than overlapping them) and create a flat, almost imperceptible seam on both sides of the garment. The result:
No raised ridge against the skin
Better stretch along the seam line (flatlock seams stretch with the fabric rather than restricting it)
Cleaner aesthetic, often used as a visible design feature
How to specify flatlock correctly
On your sportswear tech pack template, every seam should be called out with:
ISO stitch class (e.g., 607 for a 4-needle flatlock)
Needle count (3-needle vs. 4-needle—4-needle is wider, more durable, and standard for activewear)
SPI (stitches per inch) — typically 10–12 for flatlock
Thread type and weight — usually textured polyester (e.g., 150D textured poly for the looper, 75D for the needle)
Seam allowance — flatlock typically uses 6mm
Location callouts — exactly which seams use flatlock vs. coverstitch vs. bonded construction
When not to use flatlock
Flatlock isn't a universal answer. It's not appropriate for:
High-tension load-bearing seams like the gusset of leggings (use a chain stitch + coverstitch combo)
Waistbands (coverstitch or bonded elastic is stronger)
Bonded or seamless designs where adhesive tape replaces stitching entirely
A good tech pack maps each seam on the garment to the correct construction. Avoid the rookie move of writing "flatlock throughout" without thinking through load-bearing zones.
For a refresher on what goes wrong when tech packs lack this specificity, see our breakdown of common tech pack mistakes.
Labelling activewear: heat-transfer vs. woven
Labels are a small detail with an outsized effect on the wearer's experience. For activewear, this is where comfort and durability genuinely conflict—and your tech pack has to make a deliberate call.
Woven labels
Pros:
Durable—survive hundreds of wash cycles legibly
Premium hand-feel and look
Cheap at scale (a few cents each)
Cons:
Stiff edges can scratch and chafe against skin
Require a folded seam to attach, adding bulk
Itch factor is the #1 complaint in performance apparel reviews
Woven labels work for outerwear, jackets, or anywhere the label sits over a base layer. For next-to-skin activewear, they're often a poor choice.
Heat-transfer labels (HTL)
Pros:
No physical edges—nothing to scratch the skin
Lightweight and flexible, stretches with the fabric
Can be placed anywhere, including on technical fabrics
Ideal for compression wear, sports bras, and seamless garments
Cons:
Lower durability—edges can lift or crack after 30–50+ wash cycles if poorly applied
Application quality is highly factory-dependent
Slightly more expensive per unit
Printed labels (direct-to-garment)
A third option, increasingly common in premium activewear: screen-printed or DTG-printed labels applied directly to the inside of the garment. These are even softer than HTLs but require careful ink selection to survive performance-fabric care cycles.
How to specify on your tech pack
Don't just write "heat transfer label." Specify:
Label type (HTL, woven, printed)
Dimensions in mm
Placement (e.g., 50mm below centre back neck, inside)
Content (brand mark, size, fibre composition, country of origin, care symbols)
For HTLs: film type (matte vs. gloss), application temperature and pressure if known
Durability requirement (e.g., must remain legible after 50 wash cycles per care instructions)
Pulling it together: a working activewear tech pack checklist
If you're building or auditing a performance apparel specifications document, run through this checklist:
Fabric — composition, GSM, finish, stretch %, recovery %, test method
Trims — elastic type and stretch, drawcords, stoppers, eyelets, with all specifications
Construction map — every seam labelled with ISO stitch class, SPI, thread, and seam allowance
Bonded or taped seams — adhesive type, width, and placement if applicable
Labels — type, placement, content, durability spec
Measurements — graded points of measurement (POM) chart with tolerances
Care instructions — matched to fibre content and tested for performance retention
Colourway and print details — Pantone references, sublimation files if relevant
Packaging and folding spec — important for activewear's premium positioning
Activewear development is iterative. Expect 3–5 sample rounds before bulk production, especially for compression pieces. Building this level of detail into your tech pack upfront cuts the number of rounds dramatically.
Where Specter OS fits in
Compiling all of this in a spreadsheet works—until you're managing three colourways, two factories, and a fit revision on the back gusset of your leggings. That's where things fall apart.
Platforms like Specter OS centralise the entire activewear tech pack workflow: a pre-loaded CAD library for performance apparel, structured fields for stretch and recovery percentages, ISO stitch class callouts, and direct factory communication tied to each tech pack version. When your factory comments on a flatlock seam at the inner thigh, the conversation lives next to the spec—not lost in an email thread.
Specter OS offers a free tier built specifically for emerging brands navigating their first complex tech packs. If you're moving from t-shirts to performance wear, that transition is where having a single source of truth matters most.
You can explore the [case for using a fashion OS](/blog/why-fashion-brands-need-an-os
Activewear Tech Packs: How to Specify Stretch, Recovery, and Flatlock Stitching
Master activewear tech packs with detailed specs for stretch, recovery percentages, flatlock stitching, and labelling. The definitive guide for performance apparel.
Activewear Tech Packs: How to Specify Stretch, Recovery, and Flatlock Stitching
An activewear tech pack is a technical specification document that defines every material, measurement, and construction detail required to manufacture performance apparel. Unlike a tech pack for a basic t-shirt, it must specify exact fabric stretch percentages, recovery values, seam types (such as flatlock to ISO 607), and labelling decisions that affect both comfort and durability. Getting these specifications right is what separates leggings that hold their shape after 50 washes from ones that bag out after five.
Activewear is the most technically demanding category most emerging brands will ever produce. A poorly written tech pack here doesn't just cost you sample rounds—it costs you returns, reviews, and repeat customers. This guide walks through the three areas where founders most often under-specify: fabric stretch and recovery, flatlock seam construction, and labelling for skin-contact garments.
Why activewear tech packs are different
A standard apparel tech pack covers materials, measurements, construction, and trims. A performance apparel tech pack does all of that, plus it has to control for things the human body does at high intensity: stretch, sweat, friction, and repeated mechanical stress.
Factories cannot guess these things. If your tech pack just says "4-way stretch jersey" or "flatlock seams," you've handed the factory at least three different ways to interpret your design—and they'll pick the one that's easiest for them, not the one that performs best for your customer.
A complete activewear tech pack specifies:
Fabric composition with stretch and recovery percentages (not just "stretchy")
GSM (grams per square metre) and finish (peached, brushed, matte)
Seam construction by ISO code, with stitch type, SPI (stitches per inch), and thread weight
Bonded or taped seams where relevant (for compression or seamless aesthetics)
Labelling method: woven, heat-transfer, or printed directly to fabric
Care instructions matched to fibre content and finishes
If you're new to the document itself, our comprehensive tech pack guide covers the foundational structure. This article goes deeper into the activewear-specific layers.
Specifying fabric: why "4-way stretch" isn't enough
The single most common mistake on a gym wear tech pack is treating stretch as a binary feature. "4-way stretch" tells the factory the fabric moves in all directions. It tells them nothing about how much it moves or whether it returns to its original shape afterwards.
Stretch vs. recovery: the distinction that matters
Stretch is how far a fabric extends under tension. Recovery is how much of that extension it loses when the tension is released. A fabric can have excellent stretch and terrible recovery—that's the leggings-bagging-at-the-knees problem in a nutshell.
Performance fabrics should be specified with both values. For example:
Stretch: 80% widthwise / 60% lengthwise
Recovery: 95% widthwise / 92% lengthwise after 30 seconds
Recovery below roughly 90% is generally unacceptable for compression activewear. For everyday leggings or joggers, 85% is often workable. Below 80% and the garment will lose its shape within weeks.
The stretch and recovery test (ASTM D2594 / D3107)
This is the industry-standard test methodology your factory's lab can run on a swatch. The fabric is stretched to a fixed load (or a fixed extension), held, released, and measured again after a set rest period.
Specify on your tech pack:
Test method (e.g., ASTM D2594 for knits)
Required stretch % in both directions
Required recovery % after a specified rest period (typically 30 seconds and 60 minutes)
Number of cycles the fabric must endure before losing recovery (e.g., 5,000 cycles minimum)
Without these numbers, "performance fabric" is just marketing copy.
Composition guidance for activewear knits
Most activewear sits in one of these compositions:
Nylon/spandex (78/22 to 82/18) — high recovery, soft hand, ideal for compression
Polyester/spandex (87/13 to 90/10) — better moisture wicking, more affordable, slightly lower recovery
Poly/nylon/spandex tri-blends — engineered for specific performance attributes
Spandex content below 12% rarely delivers true compression. Above 22% and the fabric becomes expensive and harder to sew cleanly.
Flatlock stitching: the ISO 607 deep dive
Flatlock stitching is the seam construction standard for skin-contact performance apparel. It's not a single stitch—it's a family of stitches classified under ISO 4915 Stitch Class 600 (commonly referenced via the broader ISO 607 framework for flat seam construction).
Why flatlock exists
Conventional overlock seams (the kind on a basic t-shirt) leave a raised ridge on the inside of the garment. Under a sports bra strap, along the inner thigh of leggings, or under the arm of a running shirt, that ridge becomes a friction point. Friction plus sweat plus repeated movement equals chafing—the number-one source of activewear returns and bad reviews.
Flatlock stitches join two pieces of fabric edge-to-edge (rather than overlapping them) and create a flat, almost imperceptible seam on both sides of the garment. The result:
No raised ridge against the skin
Better stretch along the seam line (flatlock seams stretch with the fabric rather than restricting it)
Cleaner aesthetic, often used as a visible design feature
How to specify flatlock correctly
On your sportswear tech pack template, every seam should be called out with:
ISO stitch class (e.g., 607 for a 4-needle flatlock)
Needle count (3-needle vs. 4-needle—4-needle is wider, more durable, and standard for activewear)
SPI (stitches per inch) — typically 10–12 for flatlock
Thread type and weight — usually textured polyester (e.g., 150D textured poly for the looper, 75D for the needle)
Seam allowance — flatlock typically uses 6mm
Location callouts — exactly which seams use flatlock vs. coverstitch vs. bonded construction
When not to use flatlock
Flatlock isn't a universal answer. It's not appropriate for:
High-tension load-bearing seams like the gusset of leggings (use a chain stitch + coverstitch combo)
Waistbands (coverstitch or bonded elastic is stronger)
Bonded or seamless designs where adhesive tape replaces stitching entirely
A good tech pack maps each seam on the garment to the correct construction. Avoid the rookie move of writing "flatlock throughout" without thinking through load-bearing zones.
For a refresher on what goes wrong when tech packs lack this specificity, see our breakdown of common tech pack mistakes.
Labelling activewear: heat-transfer vs. woven
Labels are a small detail with an outsized effect on the wearer's experience. For activewear, this is where comfort and durability genuinely conflict—and your tech pack has to make a deliberate call.
Woven labels
Pros:
Durable—survive hundreds of wash cycles legibly
Premium hand-feel and look
Cheap at scale (a few cents each)
Cons:
Stiff edges can scratch and chafe against skin
Require a folded seam to attach, adding bulk
Itch factor is the #1 complaint in performance apparel reviews
Woven labels work for outerwear, jackets, or anywhere the label sits over a base layer. For next-to-skin activewear, they're often a poor choice.
Heat-transfer labels (HTL)
Pros:
No physical edges—nothing to scratch the skin
Lightweight and flexible, stretches with the fabric
Can be placed anywhere, including on technical fabrics
Ideal for compression wear, sports bras, and seamless garments
Cons:
Lower durability—edges can lift or crack after 30–50+ wash cycles if poorly applied
Application quality is highly factory-dependent
Slightly more expensive per unit
Printed labels (direct-to-garment)
A third option, increasingly common in premium activewear: screen-printed or DTG-printed labels applied directly to the inside of the garment. These are even softer than HTLs but require careful ink selection to survive performance-fabric care cycles.
How to specify on your tech pack
Don't just write "heat transfer label." Specify:
Label type (HTL, woven, printed)
Dimensions in mm
Placement (e.g., 50mm below centre back neck, inside)
Content (brand mark, size, fibre composition, country of origin, care symbols)
For HTLs: film type (matte vs. gloss), application temperature and pressure if known
Durability requirement (e.g., must remain legible after 50 wash cycles per care instructions)
Pulling it together: a working activewear tech pack checklist
If you're building or auditing a performance apparel specifications document, run through this checklist:
Fabric — composition, GSM, finish, stretch %, recovery %, test method
Trims — elastic type and stretch, drawcords, stoppers, eyelets, with all specifications
Construction map — every seam labelled with ISO stitch class, SPI, thread, and seam allowance
Bonded or taped seams — adhesive type, width, and placement if applicable
Labels — type, placement, content, durability spec
Measurements — graded points of measurement (POM) chart with tolerances
Care instructions — matched to fibre content and tested for performance retention
Colourway and print details — Pantone references, sublimation files if relevant
Packaging and folding spec — important for activewear's premium positioning
Activewear development is iterative. Expect 3–5 sample rounds before bulk production, especially for compression pieces. Building this level of detail into your tech pack upfront cuts the number of rounds dramatically.
Where Specter OS fits in
Compiling all of this in a spreadsheet works—until you're managing three colourways, two factories, and a fit revision on the back gusset of your leggings. That's where things fall apart.
Platforms like Specter OS centralise the entire activewear tech pack workflow: a pre-loaded CAD library for performance apparel, structured fields for stretch and recovery percentages, ISO stitch class callouts, and direct factory communication tied to each tech pack version. When your factory comments on a flatlock seam at the inner thigh, the conversation lives next to the spec—not lost in an email thread.
Specter OS offers a free tier built specifically for emerging brands navigating their first complex tech packs. If you're moving from t-shirts to performance wear, that transition is where having a single source of truth matters most.
You can explore the [case for using a fashion OS](/blog/why-fashion-brands-need-an-os