16" X 36" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 18 5/8" X 38 5/8"] flat stamped steel + Product Details Size – 4 X 12 Is CRFG2028 Width_14in

+ Product Details Size – 6"w X 10"h is the size for the duct opening measurement only

Design – Removable door/face for easy filter change & cleaning - uses a 1" thick filter

+ Product Details Size – 12"w X 20"h is the size for the duct opening measurement only

+ Product Details Size – 18"w X 36"h is the size for the duct opening measurement only

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16" X 36" Steel Return Air Filter Grille for 1" Filter Removable Frame [Outer Dimensions: 18 5 8" X 38 5 8"] flat stamped steel + Product Details Size – 4 X 12 Is CRFG2028 Width_14in + Product Details Size – 6"w X 10"h is the size for the duct opening measurement only Design – Removable door face for easy filter change & cleaning uses a 1" thick filter