K& amp N Recharger kit contains K& amp N air filter cleaner and air filter oil. It is a six step maintenance system designed to recharge any K& amp N FilterCharger air filter. Air filter oil is used to treat foam air filter elements to increase their filtering capacity. Red filter oil helps to extend engine life and prevents dirt from entering your engine. Air filter oil boosts the performance of cars and trucks. K& amp N air filter cleaner is the only cleaner formulated to clean K& amp N FilterCharger elements. K& amp N air