30" X 14" Steel Return Air Filter Grille for 1" Filter - Removable Frame - Black - [Outer Dimensions: 32 5/8" X 16 5/8"] Fixed Blades By simply measuring the width 4 X 12 Is CRFG2028 Width_14in

By simply measuring the width or the length of the vent

+ Product Details Size – 18"w X 20"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 16 5/8" width X 26 5/8" height

actual front end outer dimensions are approximately 14 5/8" width X 24 5/8" height

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30" X 14" Steel Return Air Filter Grille for 1" Filter Removable Frame Black [Outer Dimensions: 32 5 8" X 16 5 8"] Fixed Blades By simply measuring the width 4 X 12 Is CRFG2028 Width_14in By simply measuring the width or the length of the vent + Product Details Size – 18"w X 20"h is the size for the duct opening measurement only