Flanders PrecisionAire 25 In. x 30 In. x 1 In. EZ Flow II MERV 4 Furnace Filter (Copy)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 1 continuous piece of chipboard to guard against corner separation. Maximum air flow. Alleviates strain on equipment. Filters pollen, pet dander, dust lint, dust mites. For peak equipment protection and energy