What an ER Collets using common in CNC machining  

High-precision collets and precision collets. Experiment, drilling, and milling on precision instruments and equipment.

The spring collets are relatively common, and the general accuracy requirement is 3μm   and range is clamping from 0.5-34MM range,   run out TIR   3 and 5μm

      ER Collet Dimension

ER Collets