Kryptonite Keeper 12 U-Lock

The Keeper 12 U-Lock boasts a 12mm-diameter hardened-steel shackle that resists attacks by hand tools. There's also a reinforced collar over the keyway for increased protection. The Bent Foot design provides high security for low crime areas. Kryptonite's new “I” key is included. As is their $500 Anti-Theft Protection Offer. And you get a frame- or seatpost-mount carrying bracket, too.