16" X 18" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 18 5/8" X 20 5/8"] Supply Grille Think of the diameter as

Think of the diameter as a straight line from one end to the other

Actual Filter Size – 13 3/4"w x 17 3/4" x 1"

+ Product Details Size - 22"w X 34"h is the size for the duct opening measurement only

powder-coated surface is scratch-resistant

Conveniently taped together as a single piece

16" X 18" Steel Return Air Filter Grille for 1" Filter - Removable Frame - [Outer Dimensions: 18 5/8" X 20 5/8"] Supply Grille Think of the diameter as+ Product Details Size 16"w X 18"h is the size for the duct opening measurement only, actual front end outer dimensions are approximately 18 5 8" width X 20 5 8" height Actual Filter Size 15 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.