UNI AIR FILTERS. The principal of how foam air filters work is simple: Open Cell polyurethane foam is wetted with specially developed filter oil. The sticky filter oil is suspended in the path of the dirty air on the strands of the web-like cell structure of the foam. This makes it impossible for the dirt to pass through the strands. As the outer strands become loaded with dirt particles, the wetted strands down stream start trapping dirt, allowing the entire thickness to be utilized. This prevents surface loading or air restriction for 80% of the surface life of the air filter element. When the filter is sufficiently dirty it can be easily washed, re-oiled and re-used.Additonal Fitment:2006-2007 ARCTIC CAT 650 PROWLER H12006-2006 ARCTIC CAT 500 TRV AUTO2004-2006 ARCTIC CAT 650 V-TWIN2005-2009 ARCTIC CAT 500 TBX, FIS2005-2007 ARCTIC CAT 650 H12005-2008 ARCTIC CAT 400 TRV, TBX, FIS