Nominal Size: 20 x 20 x 4, Actual Size: 19 1/2 x 19 1/2 x 3 5/8 (19.5 x 19.5 x 3.63) Measure your air filter for the exact size and compare it to our actual size to ensure proper fit. Nordic Pure 20x20x4 MERV 13 Pleated AC Furnace Air Filter NOT compatible with Honeywell or Lennox 20x20x4 or an air filter with a MPR rating with an actual depth of 4 3/8. Please see Nordic Pure 20x20x5 (4 3/8 actual depth) which is compatible. Nordic Pure MERV 13 is equivalent to MPR 2200-2400 Made in the USA