16" x 18" or 18" x 16" Cube Core Eggcrate Return Air Grille Color_Red Oak Ideal for Walls & Ceilings:

Ideal for Walls & Ceilings: Designed for seamless installation in standard 10" X 8" duct openings

+ Product Details Size - 4"w X 16"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 18 5/8" width X 34 5/8" height

Actual Filter Size – 19 3/4"w x 15 3/4" x 1"

Actual Filter Size – 31 3/4"w x 19 3/4" x 1"

16" x 18" or 18" x 16" Cube Core Eggcrate Return Air Grille Color_Red Oak Ideal for Walls & Ceilings:+ Product Details Size 16" x 18" or 18" x 16" is the size for the duct opening measurement only, actual front end outer dimensions are approximately 17. 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