15.5625X19.5625X.75 actual size (16 x 20 x 1 nominal size). Our 16x20x1 air filter is an extended surface pleated filter, which outperforms ordinary air filters with medium efficiency, and are engineered for decreased pressure drop, and longer service life, which reduces HVAC equipment maintenance and energy expenses. Our 16x20x1 air filter is measured to ASHRAE test standards 52.2, which establishes that the air filter will operate as good or better than original manufacturer 16x20x1 air filters. Pleated design. MERV rated to ASHRAE standards. 654 cfm flow rate.