a filter cartridge which is environmentally friendly in that it is made up of components which are all incinerateable . the ends of a filter element are sealed using potting compound and plastic endcaps . the upper endcap , which is closed , has a pressure relief aperture associated therewith to prevent bowing . in a plugged filter condition the high - downward pressure introduced on the upper endcap is compensated by providing the cartridge with centering ribs which bottom on an associated ledge in the housing to provide a positive stop for the top endcap , preventing it from being driven down into and through the filter element . rubber gaskets are associated with the respective endcaps , and are reliably secured to the endcaps by being snap fit into grooves molded into the plastic of the endcaps . the lower endcap utilizes a simple radial seal gasket which is both highly effective and also positioned to avoid structural crushing forces on the cartridge . a keying system prevents the installation of improper filters .