The K&N E-4425 is a synthetic oil-free replacement air filter manufactured to provide exceptional filtration to your small engine or light industrial equipment. This air filter reduces restriction allowing the engine to breathe more efficiently. It is reusable, so it can be washed with K&N synthetic air filter cleaner then reinstalled to use again. It is the last air filter you will have to buy. K&N E-4425 air filter fits some Onan welders, and other applications.