The Master Lock No. 8170D U-Lock features a 6-1/8in (15cm) wide hardened steel body for maximum strength and reliability. The 1/2in (13mm) diameter double locking shackle is 8in (20cm) long and made of hardened steel, offering extra resistance to prying, cutting, and sawing. The disc key cylinder prevents picking. The Limited Lifetime Warranty provides peace of mind from a brand you can trust.