3/8-16 Threaded Blind Tophat 1018 Steel Bung Made in the U.S.A. from domestic material - very high quality. Specs: Flange diameter - 1" Flange thickness - 1/8" Non-Flanged Diameter 1/2" Total Length 1" Material: 1018 Steel Speed Dealer is your #1 source for builder parts on the web. Used for making fluid holding vessels such as gas tanks and oil bags.