Aerostar 21 1/2x23 5/16x1 MERV 11, Air Filter, Box of 4

Nominal: 21-1/2 x 23-5/16 x 1, Size: 21-1/2"x23-5/16"x3/4" 21 1/2x23 5/16x1, AC Furnace Air Filter Comparable to 3M Filtrete 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.