This return grille filter is a compatible replacement filter for the Honeywell FC40R1003 filter. It has a MERV 10 efficiency rating. Below are measurements.
Nominal size: 20x20x4-3/8
Actual size (without header): 18-1/4 x 18-1/4 x 4-3/8
Actual size (with header): 19-3/4 x 19-3/4 x 4-3/8
The Magnet logo on this page signifies that this product is a factory direct replacement to the OEM branded filter.