Roller Chain Sprocket Bore Diameter 1 in For Chain Pitch 1/2 in For Number of Strands Double Hub Type One Side Material Steel Maximum Bore Diameter 1 in Number of Teeth 21 Outside Diameter 3.62 in Pitch Diameter 3.355 in Bore Type Fixed Chain Number 40-2 Finish Black Oxide Hub Diameter 2 3/4 in Hub Projection 0.784 in Includes Set Screws Keyway Yes Keyway Width 1/4 in Length through Bore 1 5/8 in