Accumulair FC10X18A_4 MERV 6 Rating Air Filter/Furnace Filters, 10x18x1 (Actual Size) - 4 pack Actual Size of Filter: 10 x 18 x 0.75 MERV 6 Rating. Each filter lasts up to 3 months. Economical, high-capacity media makes this filter an ideal upgrade from standard fiberglass throwaways. Captures a wide variety of airborne allergens including dust, mold, pet dander, and dust mites. 4 Pack of Air Filters