The Kryptonite Keeper Standard U-Lock features a 12 mm hardened steel shackle with a double deadbolt anti-rotation design that resists bolt cutters and twisting leverage attacks. The lock's disc-style cylinder with center keyway is protected by a vinyl coating and is pick and drill resistant. It includes two stainless steel keys with an ergonomic design to reduce torque and keep them from bending or breaking. Rated at a 5/10 on our security scale, the Keeper Standard is good for quick stops in a metropolitan area, a couple hours in the suburbs or all day & overnight in rural areas. It also includes our patented Side Mount, Snap-In Bracket providing convenient U-Lock transport. The combination of these great features and our support programs including Key Safe, Anti-Theft Protection, and make Kryptonite Bicycle Locks the best choice for protecting what you value.