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Plastic bottles: it's all in the neck!

Plastic bottles: it's all in the neck!
  • When it comes to bottles and closures, the neck is the upper part of the bottle that accommodates the closure. The closure always has to fit the neck. Let's learn more about threaded necks!

To find the best possible bottle/closure combination, we need to know a number of things.


Bottle neck: definition and measurements

  • The neck of the bottle is defined by its total height, its inner diameter, its outer diameter and its thread.
  • The dimensions of a neck (expressed in mm)

Flacons en plastique : comment mesurer sa bague

28 DIN, 28 ROPP, 28/400, 28SP400: what does it all mean?

These designate different types of bottle necks

CGMI necks - 28/410, 28/400 - (US standard) and SP necks - 28SP410, 28SP400 (European standard) 28DIN, 54DIN necks 28ROPP neck (or 28PP or 28 PFP)

They consist of two numbers separated by a slash or the letters SP:

The 1st number (for ex. 28) is the OUTER DIAMETER of the neck in mm (see "T" on the plan above)

The 2nd number (for ex. 410) refers to the thread configuration and height of the neck.

These are composed of a 2-digit number indicating the OUTER DIAMETER of the neck in mm - followed by the letters DIN (Deutsches Institut für Normung).

These refer to the "Roll On Pilfer Proof" process which involves the interaction between the cap and the bottle threads. ROPP necks are designed to receive a screw cap with a pilfer band.

Cosmetics containers

(Classic / Essentiel / Tall Boston Round / SHARP, etc. * )

Chemical / detergent containers

(Lab containers / VEGA / FOME / CARRE, etc. *)

Pharmaceutical containers

(Sirop / Pharma / Veral / Alpha, etc. * )

* Fidel Fillaud bottle ranges


Some points to watch for when choosing your cap

  • Check all the dimensions of the neck, in particular the "H"dimension

In the example below, the bottom skirt of the closure makes contact with the shoulder of the bottle. This is known as bottoming-out. As soon as you tip the bottle, the liquid leaks out!

  • Check that the cap fits the neck threads
  • Check the seal system between the neck and the inside roof ofthe closure


  • Pay attention to the tolerance: Neck dimensions can vary depending on the material, the manufacturer and the manufacturing process, so it's important to pay attention to the manufacturing tolerance range of the closure AND the bottle

  • Beware of "false friends": Some necks have commonalities or similarities that can be misleading, so be careful.

  • Beware of self-sealing systems:

=> Threaded self-sealing or flip caps: to ensure the seal, the sealing lip must perfectly match the inner diameter of the neck

=> Reducer: if the neck diameter is too large, the reducer won't fit and the seal will not be ensured

  • Finally, to make absolutely sure that your bottle/closure combination works, especially if you order from different suppliers, you need to conduct testing:

=> with the solution being packaged

=> respecting the torques

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