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.

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.

Disadvantages of collets Collets are limited in the range of workpiece sizes they can accommodate and are ideally suited for repetitive jobs where the clamping requirements don't vary greatly. They are also better suited for clamping tooling with longer shanks and workpieces with consistent diameters.

A collet chuck is an alternate work holding device that also uses mechanical forces to hold a workpiece. While a collet chuck does not work with the same wide range of workpiece sizes that a jaw chuck can accommodate, it offers advantages in speed, accuracy, and productivity that may be crucial for certain jobs.