Understanding neck finishes: 24/410, 20/415 and the rest
Two numbers separated by a slash. They quietly decide whether your closure threads on, your pump dispenses correctly, and whether you can second-source a cap in a hurry.
Reading the numbers
A neck finish like 24/410 has two parts. The first number (24) is the outer diameter of the neck in millimeters, measured across the threads. The second number (410) is a SPI thread finish code that defines the thread profile, pitch, and overall height of the neck.
So 24/410 and 24/415 both have a 24mm neck, but different thread heights. A closure made for one will not seal correctly on the other.
The finishes you'll actually see
Most personal care, skincare and cosmetic SKUs land on one of about six finishes. Knowing them by sight saves a lot of back-and-forth:
- 20/410, small bottles, serums, sample sizes, dropper assemblies
- 20/415, taller version of 20/410, common on dropper bottles
- 24/410, workhorse for shampoo, conditioner, lotion, flip-tops
- 28/410, larger pumps, body washes, foaming dispensers
- 33/400, wide-mouth jars and creams
- 38/400, large HDPE jugs, industrial
Why this matters for procurement
Standardizing on common finishes means your closures are second-sourceable. If your primary cap supplier has a delay, a standard 24/410 disc-top can ship from a dozen other factories. A custom finish locks you in.
It also means tooling is amortized. We carry stock necks in the most common finishes, which keeps your MOQ at 5,000 units and your lead time at 10 weeks. A custom neck adds tooling cost and time.
Takeaway
The first number is the neck diameter in millimeters. The second is a thread style code. Standardize on common finishes (24/410, 20/410, 28/410) wherever you can, your supply chain will thank you.
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