20" x 28" or 28" x 20" Cube Core Eggcrate Return Air Grille 10in diameter + Product Details Size –

+ Product Details Size – 12"w X 18"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 16" x 20" OR 20" X 16" duct opening (measured at the opening)

+ Product Details Size - 3" Diameter is the size for the duct opening measurement only

Actual Filter Size – 11 3/4"w x 25 3/4" x 1"

Crafted from robust 20-gauge steel

20" x 28" or 28" x 20" Cube Core Eggcrate Return Air Grille 10in diameter + Product Details Size –+ Product Details Size 20" x 28" or 28" x 20" is the size for the duct opening measurement only, actual front end outer dimensions are approximately 21. 75" X 29. 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