Accumulair Gold 18x22x2 (17.5x21.5x1.75) MERV 8 Air Filter/Furnace Filters (4 pack) Nominal size is 18x22x2. Actual size is 17.5 x 21.5 x 1.75. MERV 8 Rating. Each filter lasts up to 3 months. Traps most large allergens including pollen and lint. Electrostatic charge captures airborne allergens SMALLER THAN 1 micron including fine dust, smoke, dander, mold, pet dander and dust mites. Also traps most large allergens including pollen and lint. 4 Pack of Air Filters