Accumulair Platinum 18x24x4 (17.5x23.5x3.75) MERV 11 Air Filter/Furnace Filters (2 pack) Nominal size is 18x24x4. Actual size is 17.5 x 23.5 x 3.75. MERV 11 Rating. Each filter lasts up to 3 months. Uniform pleat shape enhances dust holding capacity and maximizes air flow. Supercharged pleated panel filtering media ideally suited for capturing fine airborne allergens such as dust, smoke, dander, mold, pet dander, and dust mites. 2 Pack of Air Filters