28" X 30" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 30 5/8" X 32 5/8"] Filter Grille And is classified as Class

And is classified as Class 1 Fire Proof - B1

actual front end outer dimensions are approximately 10 5/8" width X 32 5/8" height

Mounted with a frame and bayonet joint

the actual front end outer dimensions are 7" in diameter

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28" X 30" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 30 5/8" X 32 5/8"] Filter Grille And is classified as Class+ Product Details Size 28"w X 30"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 Actual Filter Size 27 3 4"w x 29 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.