K&N 99-0638 is a 1 US gallon container of K&N Heavy Duty Air Filter Cleaner. It is the only cleaner recommended for cleaning heavy duty commercial grade air filters. This cleaner can be used to clean K&N heavy duty filters amde for large turbo diesel engines, class 6-8 over-the-road trucks, agricultural and earth moving equipment, and diesel motor homes. The 99-0638 air filter cleaner will bring your K&N heavy duty air filter to like new condition. It works to dissolve dirt and grime caught by the hybrid filter material and, then it can be rinsed out with a hose or pressure washer.