Roller Chain Sprocket, Bore Diameter 5/16 in, For Chain Pitch 1/4 in, For Number of Strands Single, Hub Type One Side, Material Steel, Maximum Bore Diameter 5/16 in, Number of Teeth 18, Outside Diameter 1.568 in, Pitch Diameter 1.44 in, Bore Type Fixed, Chain Number 25, Finish Black Oxide, Hub Diameter 1 1/8 in, Hub Projection 0.39 in, Includes Set Screws, Keyway No, Keyway Depth Not Applicable, Keyway Width Not Applicable, Length through Bore 1/2 in, Number of Set Screws 2