Roller Chain Sprocket Bore Diameter 25 mm For Chain Pitch 1/2 in For Number of Strands Single Hub Type One Side Material Steel Maximum Bore Diameter 25 mm Number of Teeth 18 Outside Diameter 3.21 in Pitch Diameter 73.14 mm Bore Type Fixed Chain Number 08B Finish Black Oxide Hub Diameter 57 mm Hub Projection 0.812 in Includes Set Screws Keyway Yes Keyway Width 8 mm Length through Bore 28 mm Number of Set Screws 2