Honeywell factory original, OEM FC100A1037 Pleated Filter, 20" x 25" x 4", MERV 11 * Static Pressure Drop (in w.c.): 0.24 * Used with Honeywell 20x25 F100 and F200 Media Air Cleaners and Aprilaire Media Air Cleaners * Nominal filter size: 20" x 25" x 4" Actual filter size: 19 7/8" x 24 7/8" x 4 3/8" * 5 pack of Honeywell factory original OEM filters