It's a ring - it's a tool - it's the jump ring opener tool! Wear this like a ring, usually on the middle finger of your left hand, for the right handed and vice versa for the left handed, but above the middle joint, so not next to your hand, but out one joint. Use it to hold one side the jump ring, while you twist it open with pliers. Has 4 slots for various sizes of jumprings, just turn around to access the different size slots (turn the ring around - not yourself!). It's like having killer fingers for gripping with! Mondo-ly useful and a must for the chain maillers.
By the each.