Honeywell 20x25x4 Furnace and A/C Filter. Part # FC100A1037. Actual Size of Filter is 19 15/16" x 24 7/8" x 4 3/8". Package of 3This Filter Replaces the 2 Cells in the 20 x 25 Honeywell Electronic Air Cleaners Actual Size of Filter is 19 15 16" x 24 7 8" x 4 3 8" To Convert from Electronic Air Cleaner to Media Air Cleaner, you will need to turn Power Switch Off for the Electronic Air Cleaner permanently and remove the 2 Cells, we highly recommend disconnecting electrical power to Air Cleaner using a qualified Technician You may need to remove plastic tab at bottom of Air