The first number refers to the thread diameter in millimeters and according to the "Glass Packaging
Institute" (GPI)/Society of the Plastics Industry (SPI) the threads diameters are expressed are: Thread 24,
28, 33, 38, and so on. This number is a universal measure and it is expressed in millimeters
The second number makes reference to the height and configuration of the thread finished. However, there
are containers in cardboard, glass, and aluminum which have different configurations and finished. This is
why it must be selected the proper cap. It not always can be a plastic cap which has the compatibility with a
glass or aluminum container, or an aluminum cap with a plastic container
The following image makes reference to the most common heights in the market in plastic containers
400 Closed with just one turn
410 Closed with one and a half tur
415 Closed with two turns
There are also other dimensions for tolerances issues in the threads’ configuration.
T - External diameter of the continuous thread.
E - External diameter of the thread’s finished, except for the thread lines.
I - Internal diameter of the finished in the narrowest possible point.
S - The distance between the higher points of the thread to the first contact with the thread’s line.
L - The distance between the higher points of the thread to the start point of the retention ring (optional).
H - It is the total height of the thread. It comes from the higher point to the surface where the shoulders of the container start.
W - Ring’s thickness which comes across the container’s neck (optional).
