12" x 20" or 20" x 12" Cube Core Eggcrate Return Air Grille 18" Diameter + Product Details Size -

+ Product Details Size - 20"w X 12"h is the size for the duct opening measurement only

+ Product Details Size – 24"w X 22"h is the size for the duct opening measurement only

Actual Filter Size – 15 3/4"w x 21 3/4" x 1"

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12" x 20" or 20" x 12" Cube Core Eggcrate Return Air Grille 18" Diameter + Product Details Size -+ Product Details Size 12" x 20" or 20" x 12" is the size for the duct opening measurement only, actual front end outer dimensions are approximately 13. 75" X 21. 75". High Quality High quality, rust free aluminum construction with smooth finished edges and counter sunk screw holes (screws included); no sharp edges.. Installation Location sidewall and ceiling. Design Cubic core eggcrate design Offers highest airflow efficiency at almost 95%, reducing