18" X 24" Steel Return Air Filter Grille for 1" Filter - Removable Frame - * Filter Included * [Outer Dimensions: 20 5/8" X 26 5/8"] 8" Diameter + Product Details Size -

+ Product Details Size - 12"w X 24"h is the size for the duct opening measurement only

Tamper-Proof Security – Features a robust design to prevent unauthorized access and protect your thermostat settings

Actual Filter Size – 11 3/4"w x 27 3/4" x 1"

Actual Filter Size – 35 3/4"w x 21 3/4" x 1"

Gymnasiums & Restaurants

18" X 24" Steel Return Air Filter Grille for 1" Filter - Removable Frame - * Filter Included * [Outer Dimensions: 20 5/8" X 26 5/8"] 8" Diameter + Product Details Size -+ Product Details Size 18"w X 24"h is the size for the duct opening measurement only, actual front end outer dimensions are approximately 20 5 8" width X 26 5 8" height Actual Filter Size 17 3 4"w x 23 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.