Description: 6pcs Spring Collets Set with C20 ER20A 100L Collet Chuck Holder CNC Milling 100mm Extension Rod Straight Shank.    Collet Specification: Material:Spring Steel;  Precision:<0.015;  Gripping Range:1/8", 5/32", 3/16", 7/32", 1/4", 9/32";  Upper Diameter:28 mm;  Bottom Diameter:25 mm;  Height:34 mm;  T.I.R.:0.0003" or 5um.  Suitable For:Boring, milling, drilling, tapping, engraving, CNC, spindle machines, and other processing;  Ground roughness is Ra0.4 Microns, plus overall fine polish.    Holder Specification: Material:40 chromium (40CR);  Hardness:HRC46-50;  Accuracy:0.01;  Shank Diameter:20mm;  Clamping Range:1-13mm;  Length:100mm.    Feature: 1. Extension rod diameter and the other parts are precision ground to eliminate imbalances, increased stability during cutting, tighten the nut directly, high rigidity, extremely powerful clamping force.  2. Shank holding collets.  3. 20mm diameter straight extended shank,applicable for deep processing.  4. Extension rod diameter, and other parts have been precision ground to eliminate unbalanc and increase stability during cutting.  5. The clamping nuts could be tighten straightly, high rigidity, strong clamping.    Package Included: 6 x Collets 1 x Chuck holder