16" X 25" Steel Return Air Filter Grille for 1" Filter - Removable Frame - Black - [Outer Dimensions: 18 5/8" X 27 5/8"] 18" Round Duct Pipe + Product Details Size – 4 X 12 Is CRFG2028 Width_14in

+ Product Details Size – 10" x 16" or 16" x 10" is the size for the duct opening measurement only

+ Product Details Size - 26"w X 24"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 20 5/8" width X 26 5/8" height

+ Product Details Size – 25"w X 20"h is the size for the duct opening measurement only

+ Product Details Size - The listed 6" diameter refers specifically to the size of the duct opening

16" X 25" Steel Return Air Filter Grille for 1" Filter Removable Frame Black [Outer Dimensions: 18 5 8" X 27 5 8"] 18" Round Duct Pipe + Product Details Size – 4 X 12 Is CRFG2028 Width_14in + Product Details Size – 10" x 16" or 16" x 10" is the size for the duct opening measurement only + Product Details Size 26"w X 24"h is the size for the duct opening measurement only