Eventually you will look out on your wing just after take-off and notice that the tab on the fuel cap is sticking up because you failed to push it down. That is if you are lucky. If not so lucky, it will have rolled off the wing because you forgot to put it in the tank after refueling. Don't ask me how I know this little bit of wisdom. Don't worry we've got you covered with this direct fit factory fuel cap.

The O-rings and stem seals around the fuel caps and cap center shafts don't last forever. When they wear, water may leak in with nasty results. Two styles of O-rings have been supplied in RV kits. They are not interchangeable. They are easily identified by color: older O-rings are black, newer ones are brown. The brown O-rings are generally auto fuel resistant, but their tolerance for the newer oxygenated auto fuels is unknown. The older (black) O-rings are no longer available.
Upgrading to the newer O-rings requires replacing the fuel cap. These newer fuel caps with brown O-rings are available and fit all the receptacles installed in the tanks.

CAUTION! 

If the T-406A replacement cap is to be used on the RV-12, it must be modified in accordance with the RV-12 construction manual (Section 37) to allow venting.