Important Note: Almost ALL furnace filters have a different "actual size" than the nominal size printed on the air filter. It's best if you measure your air filter for the EXACT size and compare it to our "Actual Size". With the 4" and 5" air filters there is a wider variance between the nominal and actual size depending on the manufacturer. If you are replacing a 4 3/8 depth 20x25x4 filter in your Honeywell unit you should order our 20x25x5 Honeywell Replacement air filter that measures 19 7/8 x 24 7/8 x 4 3/8 (19.63x24.88x4.38). Nordic Pure 20x25x4 Pleated Air Filters MERV 12 are made of electrostatically charged synthetic materials that attract and capture most airborne particulates in your home. All Nordic Pure pleated air filters are manufactured using a heavy duty, moisture resistant beverage board frame.