Actual Size: 19-1/2 x 21-7/8 x 7/8 Nominal Size: 20x22x1 Filtration Rating: MERV 10. Comparable to MPR rating 600 to 800, or FPR 5-6 rating. Blocks and Captures: Dust, pollen, mold spores, pet dander, smog, dust mites, debris.