The Forney 57903 5/16 Black Male Sure-Grip Plug is for use on Forney's Spitfire welders Miller welders and or in conjunction with Forney 57702, 5/16-Inch female Sure-Grip plug. Forney Industries is one of America's longest operating family-owned metal working product companies. Founded in 1932, Forney offers more than 5,000 products for the hardware, automotive, farm and ranch and do-it-yourself markets. If you've got metal working questions, we've got answers. We're committed to your success regardless of location size or needs. 5/16-Inch (7.94mm) black Sure-Grip plug. Proof of purchase required. neglect, negligence or accident, or that has been used in any way contrary to the purpose intended.