36" X 28" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 38 5/8" X 30 5/8"] 18in diameter + Product Details Size -

+ Product Details Size - 4"w X 16"h is the size for the duct opening measurement only

With a 6" diameter for the duct opening measurement

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+ Product Details Size – 20"w X 36"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 30 5/8" width X 32 5/8" height

36" X 28" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 38 5/8" X 30 5/8"] 18in diameter + Product Details Size -+ Product Details Size 36"w X 28"h is the size for the duct opening measurement only, actual front end outer dimensions are approximately 37. 75" width X 29. 75" height Actual Filter Size 35 3 4"w x 27 3 4" x 1" High quality High quality solid stamped steel with counter sunk screw holes (screws included) and no sharp edges Design Removable door face for easy filter change & cleaning uses a 1" thick filter. Our filter grille latch is easy to use on