18 X 1.5 THREADED BUNG AND PLUG KIT.18 X 1.5 BUNG IS 1018 mild  STEEL and radiused, PLUG IS STAINLESS STEEL. PLUG IS NOW Stainless Steel to resist rust.  MADE IN USA NOT A CHEAP IMPORT. HEX ON THE PLUG IS 1 INCH. CHECK OUR OTHER LISTING FOR MORE BUNGS AND PLUGS, We make many different styles of bungs.  We recommend that you apply a small amount of anti-seize to the threads of the plug before installation.