Accumulair Gold 12x24x4 (11.38x23.38x3.75) MERV 8 Air Filter/Furnace Filters (4 pack) Nominal size is 12x24x4. Actual size is 11.38x23.38x3.75. 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