The Flanders E-Z Flow II Series 10055.012025 Disposable Filter is designed for use with furnaces and central air units in residential and light commercial applications. These 20" x 25'' x 1" filters are constructed with a spun glass media with resin bonding and a heavy chipboard box frame. EZ Flow II filter media adhere directly to the frame, allowing it to hold its shape without a metal retainer. They are UL 900 Class 2 listed for flammability, so when clean, the filters did not flame or emit excessive sparks when tested. Product Features One-Piece Moisture-Resistant Frame Media pads and support grilles are glued to the inside perimeter of the frame. This one-piece construction results in exceptional strength and rigidity. UL 900 Class 2 Listed These filters are flame resistant. When clean, air filters do not produce flames or extensive sparks when subjected to a flame exposure test.