Fuel Cap O-Ring Seal Kits. (Requires One Kit per Fuel Cap). To order this item you will need to know the fuel cap manufacturer (i.e. Shaw or Gabb) and for all Shaw fuel caps the series number for the fuel cap (431-, 531-, or 416-). Fuel cap manufacturer and series information can be found by removing the fuel cap, turning it over, and reading the information printed on the base of the fuel cap.