Accumulair Diamond 20x25x6 (19.5x24.5x5.88) MERV 13 Air Filter/Furnace Filter Nominal Size 20 x 25 x 6. Actual Size 19.5 x 24.5 x 5.88 MERV 13 Rated. High-efficiency air filter Traps dust, allergens, and bacteria such as pollen, mold, pet dander, dust mites, and viruses More than 30 times more efficient than regular fiberglass filters Each filter lasts up to 90 days