8" x 18" or 18" x 8" Cube Core Eggcrate Return Air Grille sidewall + Product Details Size –

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

Actual Filter Size – 21 3/4"w x 29 3/4" x 1"

Actual Filter Size – 31 3/4"w x 35 3/4" x 1"

75" Width X 37

8" x 18" or 18" x 8" Cube Core Eggcrate Return Air Grille sidewall + Product Details Size –+ Product Details Size 8" x 18" or 18" x 8" is the size for the duct opening measurement only, actual front end outer dimensions are approximately 9. 75" X 19. 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