Cool idea. But it's too bulky. The metal it is made of is soft and fragile. It crumbles too easily. I find that every time I take the wrench off the bolt I have to unlock and re-tighten the lock. money thrown away. The scale is inaccurate. The side-to-side movement and opening and closing movement when you want the key to be a fixed size is too much - you round off your cheap studs and press the key onto the hard studs.