A filter arrangement includes a first filter element having opposite first and second ends; an axial length between the first and second ends; and a plurality of flutes. Each of the flutes has a first end portion adjacent to the first filter element first end, and a second end portion adjacent to the...http://www.google.es/patents/US6994744?utm_source=gb-gplus-sharePatente US6994744 - Filter arrangement and methods
