So I initially wrote: "The lock may be fine but the mounting bracket is terrible (unless I'm missing something... In which case please tell me). The silver part on the 'U' lock itself, which is supposed to slide into the black plastic mounting bracket, faces the wrong way. It's hard to describe but basically you can't clip the lock onto your bike and have sit (or hang) within that triangle made by the main bars/beams. Instead it sticks out and will get in the way of your peddling. Very annoying."But I WAS missing something. You can use the Hex Wrench that comes with it to loosen and rotate the silver part (which I think is actually called the 'spline on the shackle'). So this lock mounting thing is not a problem. Go ahead and buy it. No extra tools or anything are required. I totally take back my bad review. I'm still only giving it 4 stars because they shouldn't sell it with the shackle tightened in a position that isn't useful to anyone.