OrthrusCerberus 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. The finger hole is 1" and is elongated about 1 8" for your comfort and convenience. I usually try to take photos outside to get the colors correct, so these photos aren't great since they were taken on my desk.