ER16 Collets- ER16 Standard Collets Our ER16 collets have a capacity ranging from . 0625 - . 4062 inches or in metric sizes from 1mm up to 10mm. The number shown on the collet is the largest size that particular collet can hold, but it can be tightened to a smaller size.

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.

Your first consideration should be the size of end mills or drills you will be using most often. If you are doing smaller work you would require smaller diameter range collets. Generally you may prefer the ER16 and ER32 sizes. ​If you are doing very small work then perhaps an ER11 set would be the best choice.

The easiest way to determine what type of collet your machine has is to measure the length and diameter of the collet. All collets have a distinctive length and diameter.