Ridgid 47745 one half inch to three quarter inch NPT (Nominal Pipe Size-Threads Per Inch) dies are compatible in the Wheeler Rex 897065 Universal Die Head and the RIDGID 97065 Universal Die Head. The Die Heads can be mounted onto several different threading machines from either Ridgid or Wheeler Rex. The Dies in the head can be easily changed and if the Die Head is mounted to a machine the Die Head does not need to be removed from the machine for die changes.