US Home Filter SC40-18X18X1-6 18x18x1 Merv 8 Pleated Air Filter (6-Pack), 18" x 18" x 1",Midwest Supply Inc,SC40-18X18X1-6" /> Actual size: 17-3/4 inch x 17-3/4 inch x 3/4 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