Bolton Tools BT30 ER Collet Chuck | BT30-ER16-2.36 Finish: Black Oxide | Runout: .005mm/.0002in TIR . Works on all BT 30 machines All critical tool holder surfaces precision ground . Made from alloy structural steel hardened to 48 - 52rc | 8000 rpms | Collet nut is included Coolant thru capability | Rear thread for pull stud is M12 L: 4.27 L1: 2.36 d1: 0.630 d2: 1.100 T: M10X1.5P