True Blue 12"x20"x1" 30-Day Fiberglass Air Filter. It is effective against pollen and dust/lint. This filter reduces dust and dirt buildup in air ducts, air conditioners and furnaces. The EZ Flow II is made from heavy chipboard in a one-piece design. The filtering media is continuous filament spun glass and is made to function without a retainer, by adhering the frame directly to the media which has a light skin to make it self-retaining. UL Classified.