Helmetlok 4101 Rubberized Helmetlok is a carabiner-style lock, with a 4 digit programmable (select and set your own code) locking mechanism, designed to lock your helmet to your bike Simply open the lock, slip the carabiner through your helmet's D-Shackle, attach it to your bike and lock it, since the Helmetlok is not permanently mounted to your frame, you are free to attach your helmet to any suitable place on your bike Unlike a conventional carabiner, when the locking arm is open, it pivots outwards, allowing you to attach it to large diameter handlebars, bike frames, gear racks and grab rails, or around anything with a 1.5 inch max diameter The 4 digit locking mechanism is made from weather resistant zinc alloy and to protect your bike, the aluminum carabiner is covered with a protective plastic coating Small and compact enough to fit in your pocket or on your belt loop, don't be weighed down carrying your helmet around, enjoy the security and freedom of Helmetlok