Regarding the other comment about a pressurized fuel tank popping the cap off... If you ha ANY pressure in the fuel tank you have a much bigger problem than a potential fuel cap leak. Even 1/2 psi in a fuel tank could potentially deform or rupture a joint. If you have any pressure in the tank, your vents are clogged.

Perfect fit and seal without any machining modifications. Easily adjusted to fit the receiver ring by tightening the nut on the underside.

These fuel caps are not a direct replacement for the earlier ACS design (which were lost inflight due to inadequate rubber seal design). The new 10455 cap outside diameter is too large will require machining to fit the ACS receiver ring. After this modification, they fit nicely.

The gas cap does not mechanically lock into the ring like the 10600. Its held in place by friction against the o-ring, when you fold over the tab it squishes the o-ring, the amount of squish is adjustable with the center screw. This is significant because if the fuel tank becomes pressurized that pressure could overcome the friction and pop the cap off.