Knucklehead Panhead Sportster Vented Gas Cap Vented Cap fits most all Harley gas tanks thru 1964: both sides of original Harley "plunger rod" Fat-Bob tanks, right side on all 1965- Early 1973 Fat-Bob tanks, and all Sportster XLCH thru Early 1973. Also fits most aftermarket Sportster and Fat-Bob tanks (right side).