6" x 36" or 36" x 6" Cube Core Eggcrate Return Air Grille Compatible with Duct 8" + Product Details Size -

+ Product Details Size - 16"w X 18"h is the size for the duct opening measurement only

+ Product Details Size - 18"w X 20"h is the size for the duct opening measurement only

Actual Filter Size – 7 3/4"w x 13 3/4" x 1"

Actual Filter Size – 11 3/4"w x 33 3/4" x 1"

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

6" x 36" or 36" x 6" Cube Core Eggcrate Return Air Grille Compatible with Duct 8" + Product Details Size -+ Product Details Size 6" x 36" or 36" x 6" is the size for the duct opening measurement only, actual front end outer dimensions are approximately 7. 75" X 37. 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