Retention Knob Style Designation 21003 Taper Size CAT40 Thread Size 5/8 in-11 Angle Radius 60 Degrees Knob Outside Dia 0.5900 in Coolant Fed Coolant Through Features All Mating Surfaces Precision Ground Hardened For Maximum Longevity Manufactured to The Highest Standards For Maximum Safety and Long Life Material - Machining Carbon Steel