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

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.

There is no tool required to remove and insert a collect. It snaps in and out of the collet nut with the push of your hand. A "collet wrench" doesn't remove the collet, it removes the nut from the tool holder. Who trained you to operate a CNC router without training you how to change a collet and a bit?

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.