Changing the filters on an SMD that we bought some 25 yrs ago and drove in shed and didn't run again til now. I admit I took the old filters out a few months ago so my memory is not too clear. I ordered Wix filters and started putting them on. Question is whats supposed to be in the RH one? As I face them, the left one closest to fan is the one with the o=ringed shoulder that slips firmly into base. That seems clear enough but the RH one has just gasketed ends on the cartridge. Shouldn't there be something to seal the ends against the housing? Also the two bolts have different length shoulders. I feel the longer shouldered bolt goes in the front one?