Aerostar 16 1/2x21 1/2x1 MERV 11 Pleated Air Filter, Made in the USA, 6-Pack Nominal size: 16 1/2 x 21 1/2 x 1, actual size: 16 1/2" x 21 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 smoke Change frequency 60-90 days, made in the usa