Abstract: Multiple embodiments of a filter cartridge are disclosed, the cartridge preferably being adapted for use within a housing and including a tubular outer wall element with closures at either end, one of the closures being of unitary construction and comprising an annular ring portion for attachment to the tubular element and axially central portion. Flexible spring elements interconnect the central portion with the annular ring while being adapted for flexure into a stressed condition for urging permeable membrane portions within the ring against a filter medium contained within the cartridge for producing and maintaining a compacting force on the filter medium. Preferably, the unitary end closure cooperates with the tubular wall element and the other closure as well as with portions of the housing for assuring proper fluid flow through the filter medium.