K&N Air Filter CM-4508 K&N Air Filters are designed to achieve a virtually unrestricted air flow while maintaining filtration levels critical to engine life. The secret to their success lies in the unique characteristics of the filter medium which was originally developed by K&N all those years ago in the dust, sweat and tears of desert motocross racing. The high flow cotton gauze air filter is washable, reusable and built to last for the life of a motorcycle engine. K&N air filters consist of four to six sheets of cotton gauze layered between two sheets of aluminum wire mesh. This media is then pleated and oiled to enhance its filtering capabilities and overall performance. K&N Air Filters were created for an environment requiring maximum horsepower and enhanced acceleration in addition to protection from the dirt and dust. The result is an air filter that allows dramatically more air into an engine, is washable and reusable, and will protect your engine for the life of your ride.