Ring lock, frame lock, wheel lock; whatever you call it, this one is the best. We all use one of these. We recommend you do too.
We sell the Defender together with an integrated chain for locking to a fixed object, locking your front wheel, or locking your saddle.
Record the key number somewhere safe—if you lose your keys, shoot AXA a message and they'll send you replacements.
Side note: some of you may have seen the plywood on our door—a few bikes disappeared that night. One of them came back three months later. It was the only one that had one of these.