Nordic Pure 20 x 20 x 1/2 MERV 10 rated flat panel AC air filters consist of an internal frame bonded between flat layers of two different types of electrostatically charged filter media. The first layer is a polyester filter media which acts as a pre-filter, capturing larger airborne particulates. The second layer is a MERV rated smooth poly blend filter material which attracts and captures smaller particulates. MERV 10 1/2 filters will attract and capture dust, pollen, mold spores, pet dander and baking flour. 1/2" filters are great for apartments, window units, campers, RVs, and any air system that requires half inch air filters.