OnGuard’s Bulldog Medium is always ready for a ride. This U-lock is as strong as larger locks, yet more compact. The 13mm-thick hardened steel and OnGuard’s stout X2 double-bolt lock resist cutting, picking, pulling, bumping, and drilling. And you can carry it on your bike with the included bracket, or easily stow it in a pack or even your pocket. This mighty lock also comes with five keys, including OnGuard’s Microlight key which has a built-in light.