The abus london granit 53 230 ush bracket is a very strong durable u lock with a sold secure gold status specifically built for the uk hence the name the london granit built with a 13mm round profile shackle this abus lock features an advanced powercell double locking mechanism the powercell isolates the key cylinder from the shackle in much the same way a chinese finger trap works the harder you pull the tighter the grip on the shackle foot is adding to the powercell the granit