This holder accepts all ER20 colletsGage length is 3.75 inches longWorks on all BT30 machines .300 compression and .500 extension travel via adjustable internal springs Ideal for tapping and
reaming applications All critical surfaces precision ground Made from alloy steel hardened to 54 - 56rc Rear thread for pull stud is m12 x 1.75 MariTool Part# is BT30-TER20