K&N Air Filter. K&N replacement filters are designed for all motorcycles and ATVs to O.E.M. (manufacturer) size specifications and fit into your original O.E.M. air box without modification or jet changes. Due to design and unique high flow characteristics, K&N filters allow engines to breathe free and produce optimum horsepower. Under most conditions K&N air filters never need to be replaced - with proper cleaning and care, K&N air filters will last the life of your engine. Designed to increase horsepower and acceleration while providing excellent filtration. K&N air filters use a four-layer cotton gauze filter membrane with a large surface area to improve airflow and offer longer service intervals. K&N air filters feature an epoxy-coated aluminum wire mesh incorporated into the back-fire screen to protect the filter element.