Important Note: Almost ALL furnace filters have a different "actual size" than the nominal size printed on the air filter. Its 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. We also carry 4 7/8 and 5 1/4 inch depth filters, this is why we ask you to compare the exact dimensions. Nordic Pure 20x25x5 Honeywell Replacement MERV 8 rated air filters are what is considered the traditional 5” filter at an actual 4 3/8”. You should always measure your current filter or the housing to make sure the actual size correlates with the filter you are ordering. 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 8 furnace air filters are comparable to HVAC filters with the rating of MPR 800. This high-performance HVAC replacement filter will help keep your air conditioning and heating systems running efficiently, saving money on utilities and costly maintenance. 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.