Acme Threaded Shaft Collar, System of Measurement Metric, Bore Type Threaded, Bore Diameter 20 mm, Bore Thread Size M20x4, 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 ACME Thread, Center to Lever Top Not Applicable, Collar Construction 1-Piece, Screw Material Alloy Steel WARNING: This product can expose you to chemicals including Ethylene thiourea, which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov. -