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 12 is equivalent to MPR 1500-1900 Made in the USA