This filter is a compatible replacement filter for the Honeywell FC40R1052 return grille filter. It has a MERV 10 efficiency rating which means it will capture small indoor air particles like dust and pollen.
Nominal size: 16x20x4-3/8
Actual size (without header): 14-1/4 x 18-1/4 x 4-3/8
Actual size (with header): 15-3/4 x 19-3/4 x 4-3/8
Also known as FC40R-1052.