Aerostar 18x20x1 MERV 11 Pleated Air Filter, Made in the USA, 6-Pack Nominal size: 18 x 20 x 1, actual size: 17 1/2" x 19 1/2" x 3/4" Comparable to 3M filtrate mpr 1000 to 1200 micro allergen defense Comparable to Honeywell Allergen Plus FPR 7 Fights lint, dust mites, mold spores, pollen, pet dander, dust, and smoked