11.875x35.875x.75 actual size (12 x 36 x 1 nominal size). Our 12x36x1 air filter is an extended surface pleated filter, which outpaces standard air filters with medium efficiency, and are designed for lower pressure drop, and increased service life, which reduces HVAC equipment maintenance and energy costs. The 12x36x1 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 12x36x1 air filters. Pleated design. MERV tested to ASHRAE grades. 885 cfm flow rate.