OrthrusM. R. Mayhem
is on back order
Cerberus has a two headed brother, which made naming this defensive tool pretty easy.
I've been trying to design a single finger knuck that I like for years and finally came up with one. these are 1/2" brass and the finger hole is 1" and is elongated about 1/8" for your comfort and convenience.
These two are the first ones made. The next batch will have a little more length between the finger hole and palm support (about 3/16"). These two are comfortable for me, but I have small hands.