For TaperCAT 40 Thread Size5/8-11 Angle45ºHead Diameter0.589 Neck Diameter 0.392 Hole (Diameter)Y (0.200)L10.9880 L21.264 O-RingsN Socket Part # RKW40 Machine*Haas, Johnford * Retention knobs are not interchangable. Machines are only given as a reference, JMPP makes no guarantee this is the correct knob for your machine. Please call us at 1-800-322-7750 or email sales@jmperformanceproducts.com for knob identification help.