HELMETLOK is a carabiner-style lock with a 4-digit programmable locking mechanism to secure your helmet to your bike. Slip it through the "D" rings or slide the lock through the extension and into a "quick release" buckle.  Find a convenient place on your bike, attach & lock. The lock will fit around anything upto 38mm in diameter.  The carabiner has a rubberised coating to protect you bike from scratches.  Small & compact, the HelmetLok will fit into a jacket pocket or onto tour belt loop.