Neck Finishes Explained

When you deal with glass packaging, you can't help but come across the term neck finish and some letters and numbers once you start thinking about what type of closure to choose. Neck finishes refer to the top section of the MIRON glass, following the opening of the bottle. It is the top part that holds the closures. To ensure perfect application of your natural product using MIRON glass, glass and closure must have matching finishes.

The neck finish description consists of a few letters, followed by two numbers. So, what does that mean?

The Letters

The letters stand for the type of neck finish and say something about the technical specification of it.

DIN 18

DIN is the industry standard for dropper bottles in Europe, and DIN 18 is the German-based norm. It refers to the standard size of the neck, height and diameter. 


GL18 is the French version of the German DIN neck finish. It is normed dropper bottles. The height and diameter of the neck finish are standardized.


GPI and GCMI are the US norm of neck finishes and are followed by two numbers written like this: 22/400. The first number indicates the neck finish diameter, the second one the height and thread style. They are often used for cosmetic or para pharma with pumps or spray closures.


PP stands for Pilfer Proof. It goes with a tamper-evident closure, which includes a tear-off ring at the bottom, which breaks open when the cap is opened for the first time.

Let's take a closer look at what the numbers mean and into the most common neck finish types of MIRON Violetglass.

The Numbers

The first number indicates the distance in millimeters from one outer thread to the other. It is the diameter across the outside of the bottle's threads and the inside of the cap. Remember that glass and closure must have matching finishes.

The second number refers to the thread configuration and height of the neck. It is a thread style established by the Glass Packaging Institute and Society of Plastics Industry. The difference lies in how many threads a neck finish has and how often it wraps around the glass.

  • 400 indicates 1 thread turn
  • 410 indicates 1.5 thread turns
  • 415 indicates 2 thread turns