The closure is the smallest part of the pack and the one most likely to cause a field complaint — a leak, a hard-open cap or lost carbonation. Choosing it well is a short, structured decision. Here is how a packaging engineer specifies a closure.
1. Start from the neck finish
The closure must match the bottle neck exactly — thread profile, diameter and sealing surface. A 29/25 water neck, a PCO 1881 CSD neck and a 38 mm dairy neck each take a different cap. Get the pairing right first; see neck-finish & closure compatibility.
2. Match the application
Each product makes different demands. CSD caps must hold pressure and retain CO₂ (PCO 1881). Still water needs a light, clean seal (29/25, 48 mm). Edible oil needs a reliable wad or 2-piece seal against weeping. Dairy/juice needs hygiene and often a tamper-evident band (32/15, 38 mm).
3. Choose the seal type
One-piece caps use an integral sealing fin or liner-less design; two-piece caps add a separate liner for a tougher seal — common on oil. Read 1-piece vs 2-piece to decide.
4. Material and colour
HDPE suits most caps, PP the 55 mm lid, LDPE the 55 mm standard and the 1-piece oil cap. Material affects stiffness, sealing and cost — see the closure material guide.
5. Tamper evidence and torque
Most beverage and dairy caps need a tamper-evident band, and every line needs the right application torque — audit it with the 30-bottle method.
Specify with confidence
Delta El Nile for Industry runs 12 closure formats at +500M units/month. Find your closure, browse the caps & closures range, or build an RFQ.