JM Part Number Part Max Dia Part Max Flat Max Torque Drive Size Inches Inches Ft-lbs Inches RKW50 1.450 1.255 110 0.500 RKW50M 1.500 1.185 110 0.500 Lifetime GuaranteeMade in the USA using AISI 4150 steelExtends the life span of the Retention Knob and Toolholder