8mm X 8mm Metric Rigid Shaft Coupling One-Piece Split Clamp-Type, SteelSpecifications 5LM008008 UPC Code: 662786020131 Series: Signature Weight (lb.): 0. 10 Material: Steel Finish: BLACK OXIDE Screw Size: M3 x . 5 x 8MM Outside Diameter (in.): 2. 000 Fully metric, including clamp screwsMate two shafts with zero backlashSmooth bore protects shafts from damageSuperior torque capacity over set screw type couplingsStafford Metric Rigid Shaft Couplings are fully metric in all specifications, including the clamping screws.