Transform your central heating and cooling system into an effective air filtration unit thanks to these Filtrete Allergen Defense micro-allergen filters by 3M. These high-performance electrostatic filters attach to your furnace to ensure you and your family will be breathing the cleanest air possible. In fact, these filters attract and trap dust, pollen, smoke, pet dander, and mould spores to ensure these allergens stay far away from your lungs. This particular model measures 20 inches x 20 inches, carries an MPR of 1000 and can last up to 90 days. For best results, make sure to change your air filter seasonally. Recommended for residential use only.