17.5X29.5X.75 actual size (18 x 30 x 1 nominal size). This 18x30x1 air filter is an extended surface pleated filter, which outpaces standard air filters with medium efficiency, and are built for decreased pressure drop, and longer service life, which reduces HVAC equipment maintenance and energy expenses. Our 18x30x1 air filter is classified to ASHRAE test standards 52.2, which ensures that the air filter will capture particulate as good or better than original manufacturer 18x30x1 air filters. Pleated design. MERV classified to ASHRAE grades. 1106 cfm flow rate.