Rigid Shaft Coupling, 1 Piece Set Screw, Inch, Bore Dia. 3/8 in, Steel, Finish Black Oxide, Outside Dia. 3/4 in, Overall Length 1 in, With Keyway, Clearance Dia. 0.75 in, Screw Size 1/4 In. -20, Keyway Width 3/32 in, Max. Torque 178 in-lb, Max. RPM 3, 500 RPM