Roller Chain Sprocket Bore Diameter 40 mm For Chain Pitch 5/8 in For Number of Strands Single Hub Type One Side Material Steel Maximum Bore Diameter 40 mm Number of Teeth 18 Outside Diameter 4 in Pitch Diameter 91.42 mm Bore Type Fixed Chain Number 10B Finish Black Oxide Hub Diameter 73 mm Hub Projection 0.623 in Includes Set Screws Keyway Yes Keyway Width 12 mm Length through Bore 25 mm Number of Set Screws 2