Monkey Fist Self Defense Keychain - Red. A monkey's fist is a self defense tool, so named because it looks like a small bunched fist.It is tied at the end of a rope and has a metal ball inside making it easy to throw. String is designed to be extended or shortened for your own desired length. Convenient to carry as a keychain Specifications: Ball weight: 3oz. String Length: 8.25" .