i think most of use used the non-ring shaped gasket. remove two of the little allen head screws from the cap; like at 3 and 9 oclock. don't drop or lose em. they are tiny.
screw in the installation pins and use the length of a screw driver or similar item laid across the cap and in between the pins to turn and tighten the base into the space on the gas tank. remove the pins screw in the tiny little allen bolts.
hope this makes sense. i don't really speak mechanicish.
