Fabrics · Sportswear Encyclopedia
Polyester Interlock, Explained
The workhorse jersey fabric. Double-knit, double-faced, colour-fast, sublimation-friendly and stable enough to run at 500 kits per shift. Here is why every serious kit programme starts here — and where the GSM, yarn and finish choices actually matter.
What interlock actually is
Interlock is a specific double-knit weft-knit structure. Two sets of needles knit at the same time and their stitches are locked into each other, producing a fabric with an identical smooth face on both sides. The knit is denser and thicker than a single jersey of the same yarn count, which is why interlock feels more substantial in the hand despite being similar in weight.
The 'polyester' half of the name refers to the fibre — texturised polyester filament yarn, typically 75D/72F or 100D/144F for jerseys. Higher filament count (more, finer filaments per yarn) gives a softer hand-feel and better wicking capillary action.
GSM guide — what weight for what garment
| GSM | Best use | Notes |
|---|---|---|
| 120–135 | Kids' kits, warm-climate jerseys | Feels light, can show through under floodlight |
| 140–150 | Standard match jersey | Retail sweet spot, opaque, drapes well |
| 155–165 | Premium and pro-tier jerseys | More body, better shape retention over a season |
| 170–190 | Cold-weather long sleeve, rugby | Heavier hand, longer dry time |
| 200+ | Rugby, contact sports | Interlock rare above 200 — usually piqué or ottoman |
Why interlock beats single jersey for kits
- Double-faced — both sides look identical, so panel flipping during cutting doesn't ruin the print.
- No curling — single jersey curls at the cut edge, which slows down sewing and increases waste. Interlock cuts and stacks clean.
- Opacity — the double-knit structure blocks light better at the same GSM.
- Print performance — thicker fibre bed absorbs more sublimation dye, giving richer blacks and deeper reds.
- Shape retention — recovers from stretch better than single jersey, so the jersey still fits after 30 wash cycles.
Finishing — what the mill does after knitting
Raw interlock off the knitting machine is greasy, curled and inconsistent in width. Four finishing passes prep it for kit factories:
- Scour and bleach — remove yarn oils and neutralise any yellow tint.
- Heat-set — pass through a stenter at 180–190°C to lock the knit dimensions.
- Wicking finish — apply a hydrophilic softener so sweat spreads and evaporates instead of beading.
- Slit and roll — cut open-width, wind onto rolls at exact GSM and width tolerance (usually 155 cm ±2 cm).
How to spec interlock on a tech pack
A complete fabric callout on a jersey tech pack looks like this:
Yarn: 75D/72F texturised filament
Weight: 150 GSM ±5
Width: 155 cm (open) ±2 cm
Finish: Hydrophilic wicking, heat-set, anti-pilling grade 4
Colour: Optic white (pre-sublimation)
Wash-fastness: ISO 105-C06, grade 4 minimum
When to move off interlock
- Baselayer — use poly-spandex jersey (85/15 or 82/18) for compression.
- Rugby — use pique or ottoman knit for durability against tackling.
- Cycling — use engineered mesh + lycra panels for lightness and airflow.
- Cold weather — use brushed-back interlock or double-face fleece.
- Fashion / lifestyle — cotton-poly blends for hand-feel, but sublimation performance drops sharply.
Request an interlock swatch pack
We can ship a graded swatch pack — 130, 150, 165 and 180 GSM interlock, plus poly-spandex and mesh — so your product team can decide GSM by feel before locking a tech pack.