5/16-18 X 1/2" Threaded 1018 Steel Bung Coped for 1" Made in the U.S.A. from domestic material - very high quality. Specs: Threaded I.D. 5/16-18, O.D. 1", Rise 1/2", Cope 1" Material: 1018 Steel Speed Dealer is your #1 source for builder parts on the web. Used for welding mounts for oil tanks, gas tanks, chain guards and more.