Abus' Amparo 4850 Frame Lock bolts to your bicycle to offer convenient security for your bike. When locked, its 8.5mm-diameter steel shackle passes through the rear wheel so your bike can't be ridden away. The Frame Lock is always there when you need it and the case, the shackle and key parts of the locking mechanism are made of special hardened steel for security and durability. This lock locks the rear wheel. Be sure to get and carry a second Abus lock, like the 4850 Cable or Chain Lock (sold separately) that locks into the Frame Lock's push-and-lock port to lock your bicycle to an immoveable object.