7 pcs ER11 Collets & 13pcs Milling Chuck Collet: Material: Carbon steel & 45 # steel, Color:silver-gray & Silver This is a Precision Collets For Professionals And Hobbyists Demanding Ease Of Operation And High Quality Work Results. Hardened and precision ground. Built in self-Release design and tools will never get stuck in holder. Those ER20 collets are extensively applied to drilling, boring, milling, tapping, carving, CNC router lathe, etc. With high precision and strong holding force. 13 sizes a set can fulfill your requirements. Precision ground and hand inspected. Only the very best materials and grinding techniques used! MODEL: ER20 collet and High Quality. Type: CNC milling Lathe Tool Style: ER11 Color:silver-gray & Silver Material: Carbon steel & 45 # steel ER11 Collets: Total height: 18mm Outer diameter(Max): 11.5mm Gripping Range: 1MM to 7MM (1mm,2mm,3mm,4mm,5mm,6mm,7mm) Fits metric shank size(s): For example,1mm Collet Fits 1mm metric shank,2mm Collet Fits 2mm metric shank. Milling Chuck Collet Size: 1.2.3.4.5.6.7.8.9.10.11.12.13mm Package Contents: 7 x ER11 Collets 13 x Milling Chuck Collet