12mm Key lock. features a simple design, with an easy to use snap shut lock mechanism. Good lock that gets the job done. 6 Feet long. This is long enough to get through both wheels and the structure your locking to. Also good for locking up two bikes, however may be a little tricky to get through all wheels, but a snap to loop the frames. 12mm locks are a good happy medium, lite enough to carry, secure enough to rely on. Of coarse if someone is really out to steal your bike.... They're going to get it.