Our part # TEC-04895 Extension length should not exceed a 4 : 1 ratio of length to diameter. For example, a 1/2" shank should not extend more than 2" in front of the holder. This is only true for applications where the extension is rotating. 0.0001" runout from shank to pocket Precision ground for best T.I.R.

Techniks ER16 x 1/2" Collet Holder Extension x 140mm Length