Oxford Helmet Bag Lid LockerThe lock (not provided) is threaded down a waterproof tube that runs through the visor aperture and out of the bottom of the helmet so that you can lock it to the bike. The easiest lock to use is an armoured cable lock (such as an Oxford Revolver), but you could equally use a chain lock or a regular cable lock. Features: Secure way to leave your helmet with your bike, and keep it protected from the weather. Suitable for chains and cable locks. Handy