A filter element is includes a cylindrical media pack defining a central open volume and a longitudinal axis; a first end cap having a central aperture in flow communication with the central open volume; and a second, closed end cap having a central region closing an end of the media pack central, open...http://www.google.es/patents/US7572310?utm_source=gb-gplus-sharePatente US7572310 - Filter system; element configuration; and methods
