Material selection

Metal zip or nylon coil: cost, hand and repair

25 Oct 2026

Answer first: choose the zip by the shape of the seam it has to follow and by how the bag will be repaired — not by how it looks in a photo. A metal zip on a curve is a problem; a coil zip on a flat-faced premium pouch can look like a compromise.

Metal, polished

Metal teeth read as expensive, sound like it in the hand, and hold a straight run very well. What it costs you:

• Weight and tape width. A metal tape is wider and stiffer, so the seam allowance around the opening grows.
• Curves. Teeth do not follow a tight radius cleanly; on a rounded pouch the zip either fights the curve or the curve is straightened to suit the zip.
• Repairs. A slider can be replaced. A broken tooth means the tape is replaced, which means the bag is opened.

On a 3# polished metal zip the teeth also catch a soft lining at the end stops if the lining is not kept clear of the tape.

Nylon coil

Coil is lighter, cheaper per metre, runs around a curve without complaining, and a slider swap fixes almost every failure. What it costs you:

• Perceived value. A coil zip on a 1.2 mm structured PU pouch reads cheaper than the bag beside it, unless the teeth are finished to match.
• Puller quality. The teeth matter less than the puller: a cast metal puller on a coil zip recovers most of the premium impression, and it is the part the customer actually touches.

On a 5# nylon coil the tape is narrow, which is what you want on a small pouch where every millimetre of opening counts.

The two questions that decide it

1. Is the opening straight or curved? Straight — either works, decide on price and hand. Curved — coil, unless you are prepared to straighten the design.
2. Will the buyer’s market restrict nickel release or metal content? That is a compliance question the buyer answers, not us; if metal trim is restricted in their market, the zip becomes coil or plastic-tooth and the design has to follow.

What to write on the drawing

Zip type, tooth size, tape colour, puller type and finish, and whether the zip end stops are inside or outside the seam. That last one is where most “the zip opens on its own” complaints come from.

Orders start at 3,000 pcs, or 1,000 pcs per colour or size on stocked materials. Send the pouch drawing and we will price both zips on the same bag so you can see the difference rather than guess it.