24.5X24.5X.75 actual size (25 x 25 x 1 nominal size). Our 25x25x1 air filter is an extended surface pleated filter, which exceeds ordinary air filters with medium efficiency, and are designed for lower pressure drop, and long service life, which reduces HVAC equipment maintenance and energy expenses. This 25x25x1 air filter is classified to ASHRAE test standards 52.2, which establishes that the air filter will capture debris as good or better than original brand 25x25x1 air filters. Pleated design. MERV tested to ASHRAE classifications. 1278 cfm flow rate.