Nordic Pure 20X25X4 Merv 10 Pleated Ac Furnace Air Filters, 2 Pack. Nordic Pure Pleated Air Filters MERV 10 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. There is a metal mesh support grid bonded to the pleats for extra support. MERV 10 furnace air filters are comparable to HVAC filters with the rating of MPR 900-1000. This high-performance HVAC replacement filter will help keep your air conditioning and heating systems running efficiently, saving money on utilities and costly maintenance. The effective life of your AC air filter depends on both the inside and outside conditions in which you live. It is important to regularly change your furnace air filters especially during any home improvements for fresh, clean air in your home or office. We recommend that you change your air filter every 3-6 months to maintain maximum efficiency and economy. 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". Nominal Size: 20 x 25 x 4, Actual Size: 19 1/2 x 24 1/2 x 3 5/8 (19.5 x 24.5 x 3.63) Measure your air filter for the exact size and compare it to our actual size to ensure proper fit. If you are replacing a Honeywell or Lennox 20x25x4 or an air filter with an MPR rating with an actual depth of 4 3/8, please see our 20x25x5 (4 3/8 actual depth) Nordic Pure MERV 10 is equivalent to MPR 1000 Made in the USA