US Home Filter SC40-20X20X4 20x20x4 Merv 8 Pleated Air Filter (3-Pack), 20" x 20" x 4" Actual size: 19-3/8 inch x 19-3/8 inch x 3-5/8 inch Merv 8 tested under ashrae 52.2-2007 standards Ideal for normal air filtration and those with mild allergies Moisture resistant, heavy-duty Frame Galvanized expanded metal backing