15.5X23.5X.75 actual size (16 x 24 x 1 nominal size). This 16x24x1 air filter is an extended surface pleated filter, which exceeds standard air filters with medium efficiency, and are engineered for decreased pressure drop, and increased service life, which reduces HVAC equipment maintenance and energy costs. Our 16x24x1 air filter is measured to ASHRAE test standards 52.2, which ensures that the air filter will filter as good or better than original brand 16x24x1 air filters. Pleated design. MERV graded to ASHRAE grades. 787 cfm flow rate.