Ground Glass Joints, or Glass on Glass (GonG) joints are used to create a non-leaking seal without the use of rubber stoppers or grommets. They are used in set, consisting of the male inner piece (with a conical end, ground on the outside) and the female outer piece (ground on the inside to the corresponding dimensions). Their measurements are in millimeters (x/y) the first number is the outer dimension at the widest part of the grind, the second is the total length of the grind.
