18" X 18" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 20 5/8" X 20 5/8"] w25h25 + How To Measure A

+ How To Measure A Grille

The 1/2" white insulation

Actual Filter Size – 29 3/4"w x 15 3/4" x 1"

+ Product Details Size - 18"w X 8"h is the size for the duct opening measurement only

+ Product Details Size - 32"w X 12"h is the size for the duct opening measurement only

18" X 18" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 20 5/8" X 20 5/8"] w25h25 + How To Measure A+ Product Details Size 18"w X 18"h is the size for the duct opening measurement only, actual front end outer dimensions are approximately 20 5 8" width X 20 5 8" height Actual Filter Size 17 3 4"w x 17 3 4" x 1" High Quality High quality solid stamped steel with counter sunk screw holes (screws included) and no sharp edges Installation Location Sidewall and ceiling Design Removable door face for easy filter change & cleaning uses a 1" thick filter.