Climax Part RC-025 Mild Steel, Black Oxide Plating Rigid Coupling, 1/4 inch bore, 1/2 inch OD, 3/4 inch length, 10-32 x 1/8 Set Screw Provides torque transmision and alignment Cost effective coupling design Easily installed where major disassembly would otherwise be required Tolerance: +.0005/+.0025 Black oxide provides some corrosion resistance