The slider is the only moving part of a zipper. Its internal inlet, channel and outlet force two rows of elements to mesh or to split. The puller is only the handle. A custom zinc puller on the wrong cavity is jewellery that destroys the chain. Gauge, chain family (coil, moulded POM / Vislon, metal) and lock type are slider specifications. TrimGem University teaches them with the rest of garment hardware because the same zinc, the same plate and the same nickel test sit on snaps and pulls — and the Guangzhou catalogue will keep adding those faces.
Cavity geometry is the product
Channel accuracy on the order of 0.1 mm decides whether a #3 or #5 chain runs or chews. Mouth height and width are mill drawings (see the gauge article). Wear opens the mouth; a spread slider is the classic “burst after six months” complaint. Temporary pliers on the rear ears can pinch a loose slider closed; they also crack zinc. It is a field fix, not a factory method.
YKK and other houses stamp codes on the slider back — gauge plus chain type (coil versus Vislon-style versus metal). Read the stamp before you reorder “a #5 head.”
Lock types
- Auto-lock: a spring pin drops into the chain when the puller is released. Jackets, bags, anything that must not creep open under load. Jean laundry wants a spring that survives wash closed; washing an auto-lock slider open beats the pin.
- Semi-auto-lock: locks unless the puller is lifted to a set angle — common on apparel that still needs an easy open.
- Non-lock: no pin. Relies on garment tension. Dresses, some trousers, anywhere a lock pin would snag a fine fabric.
Lock type is independent of open-end versus closed-end. A separating ski jacket still wants auto-lock. Kids’ plastic sliders exist to reduce pinch and sharp edges; they still have a gauge.
Materials and plate
Zinc alloy (Zamak) die-cast bodies are the apparel and luggage default: sharp cavities, good plate adhesion, enough strength for a fashion puller. Unplated zinc corrodes. Brass and aluminium appear on metal-chain programmes. Stainless is marine, medical and a cost conversation. Plastic / nylon sliders are light, quiet and rust-free; they wear faster under pack load.
Plate (bright nickel, antique, gunmetal, black, PVD colour) is a corrosion and REACH story. Nickel-free programmes aim well below commodity nickel for skin-contact pulls (REACH plus brand RSLs). Salt spray (ASTM B117 / ISO 9227) belongs on metal sliders the same way it belongs on snaps. Puller-to-body strength is an ASTM D2061 / QB/T row, not a hand yank in the showroom.
How the puller attaches
A stem through the slider’s puller hole: riveted (permanent), snap-in (replaceable), or a cord loop. Stem diameters (often 1.8 / 2.2 / 2.5 mm) must match the hole. Loose stems rattle off; oversized stems crack the bridge. Logo techniques — laser, deboss, cast-in — decorate the puller, not the cavity.
Outdoor pulls should be glove-sized. Kids’ pulls should not present a sharp point. Quiet bags use a plastic slider and a rubberised puller; metal-on-metal is a noise spec.
Buying rule
Slider gauge + chain family + lock + material + plate + puller stem. Do not mix mill A’s #5 coil slider with mill B’s #5 coil because both boxes say 5. A puller is a hardware SKU on a slider, not instead of one.