18" X 36" Steel Return Air Filter Grille for 1" Filter - Fixed Hinged - [Outer Dimensions: 20 5/8" X 38 5/8"] 18" Diameter + Product Details Size – 4 X 12 Is CRFG2028 Width_14in

+ Product Details Size – 16"w X 10"h is the size for the duct opening measurement only

Our coils have a a very high PSI burst pressure

+ Product Details Size – 40"w X 10"h is the size for the duct opening measurement only

Filter Size - 19

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

18" X 36" Steel Return Air Filter Grille for 1" Filter Fixed Hinged [Outer Dimensions: 20 5 8" X 38 5 8"] 18" Diameter + Product Details Size – 4 X 12 Is CRFG2028 Width_14in + Product Details Size – 16"w X 10"h is the size for the duct opening measurement only Our coils have a a very high PSI burst pressure