US Stove UFB908 Universal Filter Box is designed to be installed on any USSC add on furnace. Specifically, it covers the blowers and allows for easy connection to the existing HVAC return duct work or to newly installed ducting. It comes with an integrated slot for a 16-Inch by 20-Inch air filter. Made of durable Galvanized steel, the UFB908 will provide-year of trouble free service. US Stove has been bringing warmth to homes across the nation for 140-year. US Stove has a wide range of Automatic Circulators, Plate Steel Heaters, Cast Iron Heaters, Pellet/Multi-Fuel Heaters and Gas Fireplaces from which to choose. The large selection of stoves and accessories will ensure warmth of your home with safe, quality products.