Roller Chain Sprocket Bore Diameter 20 mm For Chain Pitch 1/2 in For Number of Strands Single Hub Type One Side Material Steel Maximum Bore Diameter 20 mm Number of Teeth 19 Outside Diameter 3.37 in Pitch Diameter 77.16 mm Bore Type Fixed Chain Number 08B Finish Black Oxide Hub Diameter 64 mm Hub Projection 0.812 in Includes Set Screws Keyway Yes Keyway Width 6 mm Length through Bore 28 mm Number of Set Screws 2