A filter assembly wherein a housing seat (220) and a cartridge cap (330) are keyed to insure correct filter replacement procedures. The seat (220) can comprise a family of pedestals (270) and the end cap (330) can comprise a corresponding family of pedestal-insertion pockets (370). The correct filter cartridge can be easily installed (e.g., periodically replaced), by aligning the pockets (370) of the end cap (330) with the pedestals (270) in the housing seat (220), and inserting the pedestals (260) into the pockets (370).