18 X 1.5 THREADED BUNG "WITH 30` TAPER" AND PLUG KIT.18 X 1.5 BUNG IS 1018 mild  STEEL, PLUG IS STAINLESS STEEL.   THESE WILL LET YOU PUT YOUR O2 SENSOR IN MANY PLACES WHERE A STRAIGHT FITTING WILL NOT WORK.  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.  PLUG IS NOW STAINLESS STEEL to resist rust !!!!!!