Filler Neck Kit, Fuel Tank Cap Adapter, Allows a 2 In Female Fuel Cap To Be Installed On Filler Necks With Small Inside Diameters, Number of Pieces 1, Material Aluminum, For Use With Fuel Filler Necks, Includes Adapter, Instructions, and Adhesive Fuel Tank Cap AdaptersUse kits to adapt necks for use with a 2" dia. female cap. 5DYX7 is for use with small-diameter necks. 5DYX8 is for use with 2-1/2" male filler necks that have 8 threads per inch.Fuel Caps, Adapters, and Antisiphons