K&N 99-0635 is a 1 US gallon bottle of Power Kleen air filter cleaner. K&N Air Filter Cleaner is the only cleaner recommended to clean K&N cotton air filter elements. K&N Power Kleen will bring your K&N oiled cotton air filter to like new condition. It works to dissolve the dirt build up and old filter oil, then it can be washed away with water. The use of any other cleaning solution can void the filter's warranty. It is so good at cleaning greasy dirt and grime that it can also be used as an industrial strength degreaser by removing deposits from most surfaces including cotton air filters, painted surfaces, chrome, plastic and more!