Swiffer Extreme Dust Collector Air Filter, MERV 11, 20 x 20 x 1-Inch, 12-Pack Pack of 12 proprietary air filter media designed to trap and lock dust, improving air quality and filter efficiency MERV 11 rating: removes household dust, pollen, dander, lint, smoke, smog, spores and certain bacteria Electro-statically charged air filter collects over 85% of large airborne particles Each filter maintains efficiency for up to 90 days Compatible with HVAC systems requiring filters sized 20" x 20"