I don't know why I was so obsessed with making this work. Rogerlabs' original folding knuckle duster (http://www.thingiverse.com/thing:202382) just didn't quite work for me. First of all there was a problem with the size. Then there was a problem with the joints. I fixed the first, but made the second both better and at the same time worse.

This one is unitized so you can scale it up to the size of the largest ring size on the finger you intend to wear it on. So if my finger is 22mm in diameter (as it happens to be) scale it up by 22 or 2200%. Then print, assemble, and fail to wear because the joints are too big for every day wear. My next job is to make the joints closer into the body of the ring.

But, hey, you get into a fight with this thing on your hand and I guarantee the other guy will be hating life. After all, this is ABS, the same plastic LEGOs are made out of. This is like stepping on a LEGO, right across your face.