Nominal Size: 16 x 25 x 4, Actual Size: 15 1/2 x 24 1/2 x 3 5/8 (15.5 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 16x25x4 or an air filter with an MPR rating with an actual depth of 4 3/8, please see our 16x25x5 (4 3/8 actual depth) Nordic Pure MERV 8 is equivalent to MPR 800 Made in the USA