The Ridgid 66160 Alloy Pipe Dies are designed for use with OO-R, 11-R, 12-R, O-R, Ratchet Threaders or 30A, 31A 3-Way Pipe Threaders (Not Included). This unit is a British Electrical Conduit (BEC) die and provides users with a 5/8 in. nominal conduit size and a 18 in. threads per inch for right handed operation. The Ridgid 66160 requires an 11-R BEC die head for proper use.