Honeywell FC200E1029 16 X 25 Media Air Filter (MERV 13) 60 Efficiency ratings are based on American Society of Heating, Refrigerating and Air-Conditioning Engineers Standard 52.2 1999. Efficiency ranges are defined for small particles, E1=0.3 to 1.0 microns; medium particles, E2=1.0 to 3.0 microns; and large particles, E3=3.0 to 10.0 microns. Fractional Efficiency: E1=63 percent, E2=90 percent, E3=97 percent Minimum Efficiency Reporting Value (Media Filters Only): MERV 13 Static Pressure Drop (in. w.c.): 0.28 at 500 FPM