OnGuard’s Bulldog Medium DT 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, the included 4-foot steel cable is long enough that you can lock both wheels without removing them from the frame. This mighty lock also comes with five keys, including OnGuard’s Microlight key which has a built-in light.