Designed for use on most radiator valves, nipples, plugs, tank connectors etc. It has 5 different step sizes and is made from CR-MO for strength. Sizes: 3/8", 7/16", 1/2", 16MM & 21MM. Drive: 1/2". Made from CR-MO and hardened to HRC 48-55. Zinc plated for protection. This wrench is designed for making repairs to radiator valves.