Accumulair Diamond 24x30x1 (23.5x29.5) MERV 13 Air Filter/Furnace Filters (2 pack) Nominal size is 24x30x1. Actual size is 23.5 x 29.5. MERV 13 Rating Great for helping reduce airborne allergens such as bacteria, particles that carry viruses, pollen, mold spores, fine dust, and pet dander. Each filter lasts up to 3 months. Electrostatically charged filter media captures airborne allergens smaller than 1 micron!