Secure your items with the Master Lock U-Lock (8170D). It features a 6-1/8 (15cm) wide hardened steel body for maximum strength and reliability. Its 1/2 (13mm) diameter double locking shackle is 8 (20cm) long and made of durable hardened steel offering extra resistance for prying cutting and sawing. This hardened steel U-lock uses a disc key cylinder that prevents picking. It also boasts a protective vinyl coating that prevents mild scratches. This door U-lock includes a carrier bracket for ease of transportation.