The best way to check which type of collet your machine uses is to measure the length and the diameter.

Collet Life Span Collets have a life span of 400-600 hours, which roughly translates to between two and three months with the collet being used eight hours a day. When inspecting your collet, metallic damage, such as bell mouthing or burrs, should be checked with every tool change.

The standard series are: ER-8, ER-11, ER-16, ER-20, ER-25, ER-32, ER-40, and ER-50. The "ER" name came from an existing "E" collet (which were a letter series of names) which Rego-Fix modified and appended "R" for "Rego-Fix". The series number is the opening diameter of the tapered receptacle, in millimetres.

TG Collets They have a 4 degree taper which is much less than ER collets that have an 8 degree taper. For that reason, the grip force of TG collets is larger than ER collets. TG collets also have a much longer grip length resulting in a larger surface to grip with.