Honeywell FC100A1029 16 x 25 x 4 Media Air Filter (MERV 11) Nullify Imported 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. Honeywell factory original, OEM FC100A1029 Pleated Filter, 16" x 25" x 4", MERV 11 Static Pressure Drop (in w.c.): 0.24 Used with Honeywell 16x25 F100 and F200 Media Air Cleaners Nominal filter size: 16" x 25" x 4" Actual filter size: 15 7/8" x 24 3/4" x 4 3/8"