Quick answer: A neck size such as 20/410 or 24/410 tells you two things: the first number is the outside diameter of the bottle's thread in millimetres, and the second number is the thread style (400 is about one turn, 410 about one and a half turns, 415 about two turns). A cap, pump or dropper fits only when both numbers match the bottle. In our range, most caps and pumps come in 20 mm and 24 mm, serum droppers in 18 mm and 20 mm, and perfume caps in 15 mm.
A pump that does not screw onto your bottle is one of the most common, and most avoidable, mistakes first-time brand owners make.
This guide explains the numbers, shows how to measure a neck, and lists real prices for 28 caps, pumps and droppers, grouped by neck size.
What does a neck size like 20/410 mean?
The first number (20) is the "T" dimension, the outside diameter across the threads in millimetres. The second number (410) is the thread finish defined by the US Glass Packaging Institute (GPI) and the Society of the Plastics Industry (SPI). Together they describe the thread so that a closure from one maker can fit a bottle from another.
So a 20/410 bottle has a roughly 20 mm neck with about one and a half turns of thread, and needs a 20/410 cap or pump.
Many Indian listings, including ours, show only the diameter, for example "24 mm neck". In that case, confirm the thread style before buying closures from a different supplier.
What is the difference between 400, 410 and 415 threads?
The three-digit code tells you how many times the thread goes around the neck and how tall the finish is: 400 is about one turn, 410 about one and a half turns, and 415 about two turns on a taller neck. A 24/400 and a 24/410 share a diameter but are not interchangeable.
| Thread finish | Thread turns | Neck height | Where you typically see it |
|---|---|---|---|
| 400 | About 1 full turn | Short | Jars and simple screw-cap bottles |
| 410 | About 1.5 turns | Medium | Pumps, mist sprayers and dispensing caps on 18–28 mm necks (lotion, face wash, toner bottles) |
| 415 | About 2 turns, finer thread | Tall | Taller necks, often used with droppers, pipettes and some sprayers |
Sources: thread-turn definitions as published by SKS Bottle & Packaging, Paramount Global and Richmond Containers, all based on GPI/SPI standards.
Real-world threads do not always match these drawings exactly, so buy bottles and closures from the same source, or test samples first.
How do you measure the neck size of a bottle?
Measure across the outside of the threads in millimetres, round to the nearest standard size, then count how many times the thread wraps around the neck. A vernier calliper gives the most accurate reading, but a steel ruler works for a first check.
- Find the diameter. Measure straight across the widest point of the threads, not the opening. A reading of about 17.7 mm is an 18 mm neck, about 19.7 mm is 20 mm, and about 23.7 mm is 24 mm.
- Count the thread turns. Follow one thread from where it starts until it overlaps itself. About one turn suggests 400, one and a half suggests 410, two suggests 415.
- Check the closure from the inside. For a cap or pump, measure across the inside wall of the cap. A 24 mm closure will measure close to 24 mm inside.
- Test before you scale. Screw the sample closure on, fill the bottle with your actual formula, turn it upside down and leave it overnight. This catches both thread and seal problems.
Which neck sizes do Zenvista caps, pumps and droppers come in?
In our catalogue, flip-top, screw, applicator and mist-spray closures are mostly offered in both 20 mm and 24 mm, dispenser pumps, disc-tops and trigger sprayers in 24 mm, serum dropper caps in 18 mm and 20 mm, and perfume caps in 15 mm. Across the 45 size options in the table below, the median price at a pack of 100 is ₹8.91 per piece for 20 mm closures and ₹11.56 for 24 mm closures.
Prices are listed prices on zenvistapackagings.in checked on 11 October 2026, excluding 18% GST and shipping. Per-piece price = pack price ÷ pieces. Most caps and pumps also have a ₹30 sample pack. Prices may change, so confirm on the product page.
Which closure should you choose for your product?
Match the closure to how your customer uses the product: flip-tops and disc-tops for squeeze-and-pour liquids, pumps for daily-use lotions and shampoos, mist sprays for toners and hair sprays, applicator caps for scalp oils, and droppers for serums. Then pick the neck size your bottle has.
| Product | Closure that usually works | Neck sizes in our range | Example (per piece, pack of 100) |
|---|---|---|---|
| Shampoo, body wash, face wash | Flip-top or dispenser pump | 20 / 24 mm (flip-top), 24 mm (dispenser pump) | ZMPC09 black flip-top, ₹2.98; ZMPC14 black dispenser pump, ₹14.53 |
| Hair oil, scalp oil | Applicator (nozzle) cap or flip-top | 20 / 24 mm | ZMPC01 black applicator cap, ₹6.94 (24 mm) |
| Toner, face mist, hair spray, room spray | Mist spray pump | 20 / 24 mm | ZMPC07 black mist spray pump, ₹9.57 (20 mm) |
| Lotion, light cream, hand wash | Lotion pump | 20 mm (Novo), 20 / 24 mm (AS lotion pump) | ZMPC30 white Novo lotion pump, ₹19.86 |
| Face serum, beard oil, hair serum | Dropper cap | 18 / 20 mm | ZMPC32 black and gold dropper, ₹12.59 (18 mm) |
| Perfume and attar | Perfume cap over a crimped or screw spray | 15 mm | Perfume bottles and caps |
Thick creams and gels need a pump designed for higher viscosity, and very thin oils can seep through a loose flip-top hinge. Whatever you pick, test it with your real formula, not water.
What goes wrong when the neck and closure don't match?
A mismatched closure usually shows up as leaks in transit, a pump that sits crooked or loose, a dip tube that is too short or too long, or a cap that cross-threads and cracks. Most of these are avoided by matching both the diameter and the thread style, then testing a sample.
- Wrong diameter: a 20 mm cap simply will not go on a 24 mm neck, and a 24 mm cap will spin freely on a 20 mm neck.
- Right diameter, wrong thread style: a 410 closure on a 400 neck may tighten before it reaches the rim, leaving a gap that leaks when the parcel is turned over.
- Wrong dip-tube length: pumps and sprayers have a tube that should reach close to the bottom of the bottle. Too short and the last part of the product cannot be pumped out; too long and it bends and blocks. Tell us your bottle height when you order pumps separately.
- Over-tightening on the filling line: excess torque can strip plastic threads or crack a cap. Tighten until snug.
For e-commerce orders, an inner wad or seal adds a second line of defence against leaks. See our e-commerce packaging range.
How can you avoid buying the wrong caps?
Buy the bottle and closure as a matched set where possible, order ₹30 samples before a full pack, and write the neck size into your purchase records so reorders stay consistent.
- Start with the bottle. Most of our bottles are sold with a fitted cap, pump or dropper already chosen for that neck, which removes the guesswork.
- Swap closures within the same neck size to change the look. For example, replacing a basic flip-top with a gold flip-top on the same 24 mm bottle raises the closure cost from ₹2.98 to ₹11.98 per piece at a pack of 100, without changing the bottle.
- Buy in larger packs once the fit is proven. The ZMPC09 flip-top drops from ₹2.98 per piece at a pack of 100 to ₹1.58 at a pack of 1,000.
- Ask when in doubt. Share the bottle code with our team on WhatsApp (+91 96273 21000 or +91 97202 14007) and we will confirm which closures fit.
For broader planning, see our per-piece packaging cost guide for skincare startups and the packaging checklist before manufacturing.
Frequently asked questions
What does 24/410 mean on a bottle or pump?
24/410 describes a neck finish. The 24 is the outside diameter of the thread in millimetres, and 410 is the thread style, which has about one and a half turns of thread. A 24/410 pump fits a 24/410 bottle, but not a 24/400 or 24/415 bottle.
Will a 20 mm cap fit a 24 mm bottle?
No. A 20 mm closure is about 4 mm too small for a 24 mm neck and will not thread on. The diameter must match exactly, and the thread style should match too.
Are 20/400 and 20/410 interchangeable?
Not reliably. They share the same 20 mm diameter, but a 410 finish is taller and has more thread turns than a 400 finish, so a mismatched cap can sit loose, leak or not seal against the rim. Always match both numbers.
How do I measure the neck size of a bottle I already have?
Measure straight across the outside of the threads with a ruler or vernier calliper, in millimetres. Round to the nearest standard size, for example 19.7 mm is a 20 mm neck. Then count how many times the thread wraps around the neck to find the thread style.
Which neck size is most common for shampoo and hair oil bottles?
In our own range, most flip-top caps, applicator caps, screw caps, mist pumps and lotion pumps are offered in both 20 mm and 24 mm. Dispenser pumps and disc-top caps in our catalogue come in 24 mm only, which is why they are usually paired with 100 ml to 500 ml bottles.
Can I buy caps and pumps separately from bottles?
Yes. Our caps, pumps and droppers are listed separately in packs of 100, 200, 500 and 1,000, and most have a sample pack for ₹30 so you can test the fit before ordering in bulk.
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