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 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/GCMI 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. PP28 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.