OnGuard Bulldog DT U Lock and Cable Combo. For maximum security, nothing beats the combination of a rock solid U lock working in conjunction with a super sturdy steel cable. And that's exactly what you get with the OnGuard Bulldog DT U Lock and Cable Combo. OnGuard's DT U lock is operated by a laser cut key 5 are included and the OnGuard Z Key cylinder is quite the theft deterrent with its pick , pull , and drill resistant design. The U lock features an ultra hardened steel shackle that's 13mm in diameter while the braided steel cable is 4 feet long and 10mm thick to provide superb protection.