13.5X17.5X.75 actual size (14 x 18 x 1 nominal size). Our 14x18x1 air filter is an extended surface pleated filter, which exceeds standard air filters with medium efficiency, and are designed for decreased pressure drop, and extended service life, which reduces HVAC equipment maintenance and energy costs. This 14x18x1 air filter is rated to ASHRAE test standards 52.2, which assures that the air filter will perform as good or better than OEM 14x18x1 air filters. Pleated design. MERV rated to ASHRAE ratings. 516 cfm flow rate.