19.5625X24.5625X.75 actual size (20 x 25 x 1 nominal size). The 20x25x1 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 20x25x1 air filter is classified to ASHRAE test standards 52.2, which establishes that the air filter will perform as good or better than OEM 20x25x1 air filters. Pleated design. MERV rated to ASHRAE standards. 1032 cfm flow rate.