3M Filtrete Micro-Allergen Reduction Furnace Filter - 20-in x 25-in x 1-in - 1000 MPR. Get cleaner air thanks to Filtrete allergen defense micro-allergen filters by 3M. These high-performance electrostatic filters have the power to transform your central heating and cooling system into a whole-house air purifying unit! They attract and trap dust, lint, pet dander, smoke, and mould spores to ensure these particles wind up in the trash, not in your lungs. This particular model boasts a Microparticle Performance Rating of 1000 and measures 20 in. x 25 in. For best results, make sure to replace your filter seasonally (every 90 days). These filters are recommended for residential use only and have been recognized by the American Lung Association.