#25 Roller Chain Sprocket Type B 12.7mm Bore 25 Tooth, Hardened Antirust 1045
#25 Roller Chain Sprocket Type B 12.7mm Bore 25 Tooth, Hardened Antirust 1045 Steel 1/2″ bore Drive Sprockets 25B25-1/2. The surface of the sprocket is blackened, and it is corrosion-resistant and rust-proof.