Shaft Collar, System of Measurement Metric, Bore Type Round, Bore Diameter 20 mm, Bore Thread Size Not Applicable, Collar Outside Diameter 40 mm, Inside Height to Flat Not Applicable, Clearance Diameter 47.4 mm, Collar Width 15 mm, Collar Material Carbon Steel, Keyway Width Not Applicable, Collar Material Grade 1215, Keyway Depth Not Applicable, Thread Direction Not Applicable, Center to Lever Top Not Applicable, Collar Construction 2-Piece, Screw Material Alloy Steel This product contains a chemical that is regulated under California Proposition 65. Warning: This product contains a chemical known to the State of California to cause cancer. Warning: This product contains a chemical known to the State of California to cause birth defects or other reproductive harm. - Nickel (Metallic)