12" X 10" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 14 5/8" X 12 5/8"] w20h20 + Product Details Size -

+ Product Details Size - 18"w X 30"h is the size for the duct opening measurement only

Insulation – A thick blanket of fiberglass insulation provides you with an R-Value of 4

actual front end outer dimensions are approximately 27 5/8" width X 32 5/8" height

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

12" X 10" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 14 5/8" X 12 5/8"] w20h20 + Product Details Size -+ Product Details Size 12"w X 10"h is the size for the duct opening measurement only, actual front end outer dimensions are approximately 14 5 8" width X 12 5 8" height Actual Filter Size 11 3 4"w x 9 3 4" x 1" High quality High quality solid stamped steel with counter sunk screw holes (screws included) and no sharp edges Location Sidewall and ceiling Design Removable door face for easy filter change & cleaning uses a 1" thick filter. Our filter