These spark plugs are for the antique motorcycle enthusiast who enjoy riding. Spark plugs are air cooled with a heat range #3. Comes with the Knucklehead Service and Parts manual. Includes the brass top nuts which are used with earlier or hood style terminals and sealing gaskets. Terminal nut is removable. Plug set has a round feeler gauge. Replica spark plugs have a 1-1/8 inch hex shape and 18mm thread. Set of two. FITS HARLEY: 1936-1947 EL, 1937-1947 UL, 1941-1947 FL,
