Standard ANSI 50A13 sprocket with a 40mm bore. **Solid in 20's, Priced Individually** ANSI Type "A" sprockets are hubless sprockets with a stock bore. These are also commonly referred to as plate sprockets. All Type "A" Nitro sprockets have a black oxide finish. Size Chain: #50 # of Teeth: 13 Bore (D1): 5/8 Outside Diameter (de): 2.911 Sprocket Thickness (B1): 0.343 Manufactured from 1018 mild steel.