Serfas CL-501 Combo Lock 12mm: You don't have to worry about losing your bike lock key with the Serfas Combo Lock. This self-coiling cable stays out of the way on your bike or in your pack, and the five-digit combination lock eliminates the need for a small, ever-so-quickly losable key. Use the included bike attachment to secure the Combo Lock on your bike frame while you ride.