Fatz Fabrication Filter Cleaning KitK&N Filter Cleaning Kit. Fatz Built Filters are unique in their design with specific off road application in mind. We do however recommend the use of K&N Filter cleaning kits for our oiled filters. Kit includes the cleaner and oil an an aerosol can to ensure good atomization of the oil to ensure good coverage of the filter element and avoidance of over oiling. Fatz Built filters can be cleaned numerous times before replacement which makes ongoing