Arlen combined clean sculpted billet styling with high tech filter technology used in Formula 1, Nascar and the aerospace industry. These filters use a laser cut 304 series stainless steel medical grade micronic cloth in stead of traditional paper as filtering media. This guarantees a consistent flow under all conditions including extreme heat, presence of water and cold start ups. Best of all is that you can just simply wash the filter element and use it over and over again. Fits all Evolution Sportster, Evolution Big Twin, Twin Cam and Milwaukee Eight engines.