... 2,high precision cnc tech 3,black oxide anti-corrosion 4,large production, large stock Black Oxide Sprocket 1, all made by ... . high precision and good wear resistance. 2, surface treatment is black, galvanization, chroming and colored drawing. 3, material is A3\C45 ... requirement. ANSI C45 industrial machining hard teeth transmission chain drive black oxide sprocket wheel