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/US7252704?utm_source=gb-gplus-sharePatente US7252704 - Filter arrangement and methods
