Ridgid 48610 5/16-inch 500B High Speed Bolt Dies 48610 Dies, 500B 5/16 Nc Hs This item is used for Handtools & Tool Organizers ,Other Hand Tools This product manufacture by United States Bolt Dies for 500B and 531, 532, 541 and 542 Die Heads RH High Speed 5/16" rod size 18 TPI