Some filter elements come with two gaskets in the package, one wider than the other. Use whichever one fits your particular canister lid the best. I believe that Fram and AC canisters were able to use the same filter cartridge, but they required a different cover gasket. The diameter of the cartridge might not completely fill the canister, but the rubber grommets are supposed to be a snug fit on the center standpipe. If you clean the canister well and shine a bright light on the standpipe, you should be able to see a tiny hole (1/16") in the pipe a few inches below the top. That is the flow control restrictor that prevents the filter from starving the engine for oil as it bypasses some of the oil directly back to the pan. (Assuming you have the filter with the small supply and return lines).
Jerry
