10" x 18" or 18" x 10" Cube Core Eggcrate Return Air Grille 18" Round Duct Pipe + Product Details Size –

+ Product Details Size – 24"w X 36"h is the size for the duct opening measurement only

Ideal for Walls & Ceilings: Designed for seamless installation in standard duct openings

+ Product Details Size – 10"w X 34"h is the size for the duct opening measurement only

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Actual Filter Size – 24 3/4"w x 25 3/4" x 1"

10" x 18" or 18" x 10" Cube Core Eggcrate Return Air Grille 18" Round Duct Pipe + Product Details Size –+ Product Details Size 10" x 18" or 18" x 10" is the size for the duct opening measurement only, actual front end outer dimensions are approximately 11. 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