K&N is a pioneer in the washable sports air filters market. Their air filters are present in every sector of car and motor sports. The most popular air-filter brand of the United States.Replacemant filters fit perfectly into the factory filters, facilitating engine air supply, which increases a 5-8%increase in power. K&N direct filters, which provide the engine with colder air, enhances its performance. In Nascar, Indicar and Le-Mans, most car banks & n sports air filters are used. may.