A hexagon Allen key, is a simple tool used to drive bolts and screws with hexagonal sockets in their heads. The tool is formed of a single piece of hexagonal steel, with blunt ends that are meant to fit snugly into the screw's socket. It is bent in an "L" shape with unequal arms. For in-hex screws. Hexagon socket key with ball end and holder. Chrome vanadium steel 59CrV4. Gunmetal finish.