How to Read a Bottle Neck Finish Code (28-410, 38-400, 45-400) and Match the Right Cap
Quick answer
A neck finish code has two parts. The first number is the nominal thread diameter in millimetres (28, 38, 45); the second is the thread style from the industry 400/410/415 series, which sets how tall the finish is and how many turns the thread makes. A cap only fits a bottle with the same diameter and the same series: a 38-400 cap is made for a 38-400 neck. Then choose the liner and, if needed, a child-resistant version of the same finish, and confirm fit, torque and seal on samples.
Quick facts: PET Bottles for Candy and Pharmaceutical Packaging
- Indicative unit price: about US$0.15–0.60 per bottle with cap at 500 pcs using an existing mould; a new custom mould adds a one-off tooling cost. This is a guide, not a quotation: the final price depends on size, material, print colours, finish and order quantity.
- MOQ: typically from 500 pcs per size and artwork; the confirmed minimum depends on material, print method and features and is stated on the quotation.
- Lead time: Physical samples 5–7 working days after artwork is confirmed; bulk production 20–30 days after sample approval.
- Who makes it: BestPackFactory’s own factory in Longhua District, Shenzhen, China. Free dieline and artwork proof within 24 hours. See real samples and videos.
- Specifications and quote: PET Bottles for Candy and Pharmaceutical Packaging · Request a quote
Why the neck finish matters
Most bottle problems that reach customers are closure problems: caps that back off in transit, liners that do not seal, child-resistant caps that click but do not lock. Almost all of them start with a mismatch between the bottle neck and the closure. Our supplement packaging guide compares formats such as bottles, pouches and blisters; this article covers only how to read the neck finish code and pick a closure that fits it.
How to read the code
Neck finishes for plastic and glass containers follow a widely used industry numbering system. A code such as 38-400 is read as:
- 38 — the nominal outside diameter of the thread, in millimetres. It is a nominal size; the actual measurement is typically slightly less, so measure with calipers only to identify the family, not to design a cap.
- 400 — the thread series, which sets the finish height, thread pitch, the number of turns and where the sealing surface sits.
Common thread series
| Series | Thread turns (approx.) | Finish height | Typical use |
|---|---|---|---|
| 400 | about 1 | Short | Supplement, candy and pharmacy bottles and jars with screw caps or CR caps |
| 410 | about 1.5 | Medium | Liquids with pumps, sprayers, disc tops and flip caps; personal care |
| 415 | about 2 | Tall | Narrow tubes and tall closures such as some droppers and treatment pumps |
A 28-400 and a 28-410 share the same diameter but not the same height or thread length, so their caps are not interchangeable. Always match both numbers.
Typical neck sizes by product
These pairings are commonly seen in the market and are a starting point, not a rule. Confirm against the exact bottle drawing.
| Product | Typical bottle size | Commonly seen finish |
|---|---|---|
| Capsules or tablets, small count | roughly 60–150 cc | 33-400 or 38-400 |
| Capsules or tablets, large count | roughly 150–300 cc | 38-400 or 45-400 |
| Gummies and soft chews | roughly 150–500 cc | 45-400, 53-400 or wider |
| Hard candy and sweets in jars | varies | Wide-mouth 63-400 and above |
| Liquid supplements with dropper or pump | roughly 30–250 ml | 18-410, 20-410, 24-410 or 28-410 |
Wider mouths make it easier to pour or reach gummies, but they need a larger cap, a larger liner seal, and a CR closure if required, all of which add cost.
Choosing the closure
- Match the finish. Diameter and series must match the bottle.
- Decide child resistance. Many supplement products, especially those containing iron, are expected or required to use child-resistant closures in some markets. CR caps such as push-and-turn designs are made for specific finishes, and the closed package must pass the child-resistance test your market requires (for example, ISO 8317 for reclosable packages, or the US Poison Prevention Packaging Act test protocol). Confirm with your regulatory adviser.
- Choose the liner. Common options are a pressure-sensitive liner, a foam liner, or an induction seal liner that bonds a foil membrane to the bottle lip for tamper evidence and moisture barrier. The liner must suit the bottle material and the product.
- Add tamper evidence. Induction seals, neck shrink bands or caps with a tamper band are the usual choices. A tamper-band cap needs a neck with the matching bead.
- Plan for desiccant and cotton. If you add a desiccant canister or cotton coil, check it passes through the neck opening.
- Check torque. Ask for the recommended application torque for the closure and finish, and test removal torque after capping.
What to send in your RFQ
- Product type, piece size, count per bottle and fill weight or volume.
- Preferred bottle shape, colour (clear, amber, white, opaque) and size if known.
- Neck finish if fixed by your capping equipment or existing caps.
- Closure type: standard screw cap, CR cap, flip cap, dropper or pump; and colour.
- Liner or seal: pressure-sensitive, foam, induction seal; tamper band or shrink band.
- Desiccant or cotton, and whether a label or shrink sleeve will be applied.
- Target markets, quantity per design and artwork status.
Common mistakes
- Ordering bottles and caps separately with only the diameter specified.
- Assuming a 400 and 410 cap of the same diameter are interchangeable.
- Choosing a CR cap after the bottle is tooled and finding the finish does not match.
- Specifying an induction seal liner without confirming the sealing equipment and bottle material.
- Choosing a neck too narrow for gummies or the desiccant.
Test before full production
Request matched bottle and cap samples. Fill them with your product, cap them at the recommended torque, and check: the seal or induction liner bond, removal torque after a few days, leakage or moisture ingress, CR function if used, and how the cap looks with the label or sleeve applied. Then lock the bottle drawing, neck finish, closure and liner into the purchase order.
Frequently asked questions
What does 38-400 mean on a bottle?
38 is the nominal thread diameter in millimetres and 400 is the thread series. The 400 series is a short finish with about one full turn of thread. A 38-400 cap is made to fit a 38-400 neck.
Can I use a 28-400 cap on a 28-410 bottle?
Usually not. Both have the same nominal diameter, but the 410 finish is taller with about one and a half thread turns, so a 400 cap may not seal properly and a 410 cap on a 400 neck can bottom out. Match both numbers.
Which neck sizes are common for supplement bottles?
Small capsule and tablet bottles are often seen with 33 mm or 38 mm finishes, larger capsule bottles with 38 mm or 45 mm, and wide-mouth gummy and candy jars with 53 mm and above. Treat these as typical and confirm against the bottle you choose.
Does a child-resistant cap need a special bottle?
It needs a bottle whose neck finish matches that CR closure, and the closed package must pass the child-resistance test required in your market. Choose the closure first and confirm the matching bottle finish.
What is the MOQ for custom PET bottles?
At BestPackFactory the MOQ is 500 PCS per design. Bottle, closure and cost for your specification are confirmed in the quotation.
Related pages
Prepare a quote-ready packaging brief
Send your product, fill count or weight, target bottle size, neck finish if known, closure type, liner or seal, desiccant, market and labelling plan, quantity per design and artwork status. Every product is made in BestPackFactory’s own factory and the MOQ is 500 PCS per design; specifications, documents and schedule are confirmed in the quotation. You can also reach Lisa on WhatsApp +86 158 8653 0985 or at lisa@colorprintingpackage.com.
Request a project quote