36" X 20" Steel Return Air Filter Grille for 1" Filter - Fixed Hinged - [Outer Dimensions: 38 5/8" X 22 5/8"] Insulated Line Set Actual Filter Size – 29 4 X 12 Is CRFG2028 Width_14in

Actual Filter Size – 29 3/4"w x 19 3/4" x 1"

Design – Removable face for cleaning and access to damper - wooden damper for airflow shutoff control

+ Product Details Size - 24"w X 2"h is the size for the duct opening measurement only

+ Product Details Size – 4"w X 12"h is the size for the duct opening measurement only

For example

36" X 20" Steel Return Air Filter Grille for 1" Filter Fixed Hinged [Outer Dimensions: 38 5 8" X 22 5 8"] Insulated Line Set Actual Filter Size – 29 4 X 12 Is CRFG2028 Width_14in Actual Filter Size – 29 3 4"w x 19 3 4" x 1" Design – Removable face for cleaning and access to damper wooden damper for airflow shutoff control