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

+ Product Details Size – 24" x 24" is the size for the duct opening measurement only

The total outer size of this grille is the listed size plus 2 and 5/85"

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

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

Actual Filter Size – 17 3/4"w x 27 3/4" x 1"

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