Minipleat Air Filter Without Gasket Nominal Filter Size 18x24x4 Nominal Height 18 In. Nominal Width 24 In. Nominal Depth 4 In. Filter Efficiency 80 Percent to 85 Percent MERV 13 Air Flow 500 fpm Initial Resistance 0.45 in WC Final Resistance 1.5 in WC Filter Pack Enclosure Beverage Board Frame Material 100 Percent Synthetic Media Max Air Flow 1500 cfm Max Temp 150 Degrees F Standards UL 900