nordic pure 20x20x5 (4-3/8 actual depth) merv 13 plus carbon honeywell fc100a1011 replacement pleated ac furnace air filter, 2 packThe MERV 13 Plus Carbon air filter is a convenient pleated air conditioner furnace filter that has been impregnated with activated carbon and will help to eliminate unwanted pet and home odors as well as reduce the dust in your home or office. With each pass through the pleated filter, the air in your living environment improves. Our high efficiency activated carbon filter will absorb hold odors from smoke, pets, garbage, bathrooms, litter boxes and cooking in the millions of microscopic carbon pores. Odorous gases and vapors (VOC) are attracted to and held by the activated carbon material. The MERV 13 electrostatic filters help trap airborne particles to protect your family from pollen, household dust, mold spores, and dust mites. The Nordic Pure anti-microbial media will not permit the growth of bacteria or mold, therefore, making your breathing environment healthier. It can be installed in practically any HVAC system without modifications. The Nordic Pure anti-allergen pleated air filter has a Minimum Efficiency Reporting Value(MERV) of 13 which means that it will collect more than 90-Percent of 1.0-10.0 microns of contaminants, and up to 95-Percent of .30-1.0 microns of contaminants. Nordic Pure air filters have an actual size that is a fraction of an inch smaller than the nominal size. With the 4 and 5 air filters there is a wide variance between the nominal size and actual size. Almost ALL filters have a different actual size than the nominal size printed on the filter so it is best if you measure your filter for the EXACT size and compare it to our "Actual Size. This is why we ask you to measure your filter so you aren't surprised if the filter doesn't fit! Our MERV 13 four or five inch air filter should be changed at least every 6 months depending on your environment.