The Horti-Control Dust Shroom has a message for air pollutants and contaminants: "None shall passs!" The 6-inch Dust Shroom is a washable, reusable, HEPA air filter made out of foam. The Dust Shroom filters out virtually all uninvited airborne contaminants and can be used in indoor gardens, fans, ice boxes, ducting, air-cooled reflectors, and more. When the Dust Shroom is loaded up to capacity with grimey pollutants, just throw it in the washer! After a wash, the Dust Shroom will be ready for another round of service. The 6 inch Horti-Control Dust Shroom is made in the U.S.A. and has a five-year warranty from Horti-Control. None shall pass!