Roller Chain Sprocket Bore Diameter 20 mm For Chain Pitch 3/4 in For Number of Strands Single Hub Type One Side Material Steel Maximum Bore Diameter 20 mm Number of Teeth 12 Outside Diameter 3.37 in Pitch Diameter 73.6 mm Bore Type Fixed Chain Number 12B Finish Black Oxide Hub Diameter 53 mm Hub Projection 0.94 in Includes Set Screws Keyway Yes Keyway Width 6 mm Length through Bore 35 mm Number of Set Screws 2