28" X 32" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 30 5/8" X 34 5/8"] Aluminum + Product Details Size – w6h6 actual front end outer MFFG410-1

+ Product Details Size – 36"w X 12"h is the size for the duct opening measurement only

+ Product Details Size - 8"w X 24"h is the size for the duct opening measurement only

Think of the diameter as a straight line from one end to the other

+ Product Details Size - 20"w X 28"h is the size for the duct opening measurement only

28" X 32" Steel Return Air Filter Grille for 1" Filter Removable Frame [Outer Dimensions: 30 5 8" X 34 5 8"] Aluminum + Product Details Size – w6h6 actual front end outer MFFG410 1 + Product Details Size – 36"w X 12"h is the size for the duct opening measurement only + Product Details Size 8"w X 24"h is the size for the duct opening measurement only