The Kryptonite Kryptolok Combo U-Lock features a 12mm hardened high grade carbon alloy steel shackle with a BentFoot design that resists bolt cutters and twisting leverage attacks. The lock uses a 4-digit resettable combination that is protected by a rotating dust cover. It has anti-rattle bumpers to reduce noise during transport. Rated at a 6 / 10 on our security scale, the Kryptolok Combo U-Lock 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 multi-location U-Lock transport. The combination of these great features and our support programs including Combo Safe, Anti-Theft Protection, and Lifetime Warranty make Kryptonite Bicycle Locks the best choice for protecting what you value.