Aerostar 18x20x1 MERV 13 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 1500 to 1900 ultimate allergen defense Comparable to Honeywell Allergen Elite FPR 10 Fights lint, dust mites, mold spores, pollen, pet dander, fine dust, smoke, viruses, and bacteria