NEMA 14-50P 4 Prong 50 amp 250 Volt male plug; NEMA 6-50R 3 Prong 50amp 250Volt welder female receptacle connector. Welder plug adapter. Welding power cord with NEMA 6-50R connector is widely used for 3-prong 220/240V ARC TIG MIG welding machine.
eBay