Accumulair Platinum 18x22x1 (17.5x21.5) MERV 11 Air Filter/Furnace Filters (6 pack) Nominal Size 18 x 22 x 1. Actual Size 17.5 x 21.5 x 0.75 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 - attracts particulates like dust to a TV screen. MERV 11 Rating