Roller Chain Sprocket Bore Diameter 1 1/2 in For Chain Pitch 1/2 in For Number of Strands Single Hub Type One Side Material Steel Maximum Bore Diameter 1 1/2 in Number of Teeth 21 Outside Diameter 3.62 in Pitch Diameter 3.355 in Bore Type Fixed Chain Number 40 Finish Black Oxide Hub Diameter 2 3/4 in Hub Projection 0.716 in Includes Set Screws Keyway Yes Keyway Width 3/8 in Length through Bore 1 in Number of Set Screws 2