Shaft Collar System of Measurement Inch Bore Type Round Bore Diameter 2 1/2 in Bore Thread Size Not Applicable Collar Outside Diameter 3 3/4 in Inside Height to Flat Not Applicable Clearance Diameter 4.06 in Collar Width 7/8 in Collar Material Aluminum Keyway Width Not Applicable Collar Material Grade 6061 Keyway Depth Not Applicable Thread Direction Not Applicable Center to Lever Top Not Applicable Collar Construction 2-Piece Screw Material Carbon Steel