The K&N E-4550 is a synthetic, oil-free direct replacement air filter intended for use on select Onan generators. It was specifically designed to be the ideal replacement for generators, providing excellent filtration and high air flow. This air filter allows your engine to breathe more efficiently by reducing restriction. It uses a special synthetic hybrid media to allow for depth loading of dirt and contaminants into the filter fibers. That means this filter can go for long intervals between servicing. When the filter does need to be serviced, it can simply be washed and reused.