Collet System ER Collet Series ER20 Shank Type Taper Shank Taper Size CAT50 Projection Decimal Inch 4 DIN Coolant option standard All Ground Body Factory Balanced to save spindle life, tool life and increased productivity Threaded through holes for a backup screw tool stop or coolant through when removed Wrench not included Premium balanced to G25 At 30,000 rpm.