This pack includes three Ford nut compression fittings with a 1/2 x 20 UNF thread. They are compatible with Stromberg 97, 81, 48, and 40. The pack comes with ferrules and should be used exclusively with 1/4-inch OD solid fuel lines. These fittings fit most Ford flathead fuel pumps, except for the 1951-53 1BA pump, which requires 1/8th NPT fittings.