The most common sizes of bottle caps
Standard sizes for caps, stoppers and caps are usually 18/410, 20/410, 24/410, 28/410, 24/415, 24/400, etc. where:
The first number indicates the inside diameter of the cap (in millimeters), measured immediately at the stopper opening
The second number represents the GPI of the thread, which refers to the height of the cap and the type of thread on the cap and container (bottle or jar). GPI stands for Glass Packaging Institute, which has standardized nqvoy shapes for bottles and jars over the years.
Before choosing a cap, you need to know the correct size. Caps are not replaceable, 28/400 caps do not seal well against 28/410 thread bottles.