The fuel filter felt washes are glued on the top and bottom of the fuel filter. It is a tight fit. Use some grease on the felt so it will slip easily in place. The large, round, square profile o-ring fits into the groove in the housing top. Keeping it in place while installing the canister can be troublesome. I usually use some grease to hold it into place, wipe off excess before tightening down the canister bolt.