Roller Chain Sprocket Bore Diameter 20 mm For Chain Pitch 5/8 in For Number of Strands Single Hub Type One Side Material Steel Maximum Bore Diameter 20 mm Number of Teeth 21 Outside Diameter 4.59 in Pitch Diameter 106.51 mm Bore Type Fixed Chain Number 10B Finish Black Oxide Hub Diameter 76 mm Hub Projection 0.623 in Includes Set Screws Keyway Yes Keyway Width 6 mm Length through Bore 25 mm Number of Set Screws 2