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

+ Product Details Size - 12"w X 28"h is the size for the duct opening measurement only

Actual Filter Size – 29 3/4"w x 9 3/4" x 1"

Universal Fit – Measures 6" wide x 3-1-13/16" high x 3-1/8" deep

75" Width X 9

+ Product Details Size – 30"w X 28"h is the size for the duct opening measurement only

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