This is a standard grade furnace filter of the same type that has been protecting furnaces and central air conditioners around the world for over 50 years. The filtering medium is continuous filament spun glass. The frame is made with one continuous piece of chipboard to guard against corner separation. For peak equipment protection and energy efficiency, these filters should be changed monthly in periods of high use. Buy a case and be set for the year!
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.