Flatlock vs Overlock — What Activewear Buyers Should Spec

Seam choice changes comfort, bulk under compression and failure mode. Spec it — do not leave it to ‘factory standard’.

Quick comparison

	Flatlock	Overlock
Hand under stretch	Lower profile, less chafe risk	More ridge / bulk
Common use	Legging side seams, bra perimeter zones	Joins, interiors, cost-sensitive lines
Spec risk	Needs skilled operators + correct needle	Easier to run; watch bulk under compression

Activewear seam strength test — what to write

Put method, specimen, minimum force and acceptance into the tech pack / quality agreement. Pair with needle damage and stitch density checks. See AQL 2.5.

Tech pack requirements

Seam map by zone (not one global ‘flatlock’).
Stitch type / SPI / needle.
Photo of approved seam on PPS.

Checklist: tech pack requirements.

ZIESHINE path

Library styles already run production-intent seams. For OEM changes, brief via activewear manufacture hub and lock at PPS.

Seam choice follows the garment desk: leggings · bras · activewear. Fabric hand via Fabric Selector.

FAQ

Is flatlock always better?

For next-to-skin compression, flatlock often feels better. Overlock can be right for bulk-critical or cost-sensitive seams.

Should every seam be flatlock?

No — mix constructions by zone. Spec by seam map in the tech pack.

How do I test seam strength?

Agree method and minimums (e.g. grab / seam slippage) on the quality agreement before bulk.

Does seam type affect AQL?

Defect classification should call out open seams, skipped stitches and needle damage explicitly.