30" X 18" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 32 5/8" X 20 5/8"] Grilles Actual Filter Size – 33

Actual Filter Size – 33 3/4"w x 35 3/4" x 1"

Size - 10"w X 10"h is the size for the duct opening measurement only

Actual Filter Size – 31 3/4"w x 19 3/4" x 1"

And Meets/Beats ASTM B280 Standard

With these options

30" X 18" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 32 5/8" X 20 5/8"] Grilles Actual Filter Size – 33+ Product Details Size 30"w X 18"h is the size for the duct opening measurement only, actual front end outer dimensions are approximately 32 5 8" width X 20 5 8" height Actual Filter Size 29 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.