Aerostar 20x24x4 MERV 11, Pleated Air Filter, 20 x 24 x 4, Box of 6, Made in the USA Nominal: 20 x 24 x 4 Size: 19 3/8"x23 3/8"x3 3/4" 20x24x4, AC Furnace Air Filter High Capacity Comparable to 3M Filtrete MPR 1000 to 1200 Micro Allergen Defense Comparable to Honeywell Allergen Plus FPR 7 Fights lint, dust, dust mites, mold spores, pollen, pet dander, and smoke.