18" x 36" or 36" x 18" Cube Core Eggcrate Return Air Grille 8in diameter Actual Filter Size – 13

Actual Filter Size – 13 3/4"w x 17 3/4" x 1"

+ Product Details Size - 10"w X 12"h is the size for the duct opening measurement only

14"w X 4"h Is The Size For The Duct Opening Measurement Only

actual front end outer dimensions are approximately 10 5/8" width X 12 5/8" height

+ Product Details Size - 4"w X 10"h is the size for the duct opening measurement only

18" x 36" or 36" x 18" Cube Core Eggcrate Return Air Grille 8in diameter Actual Filter Size – 13+ Product Details Size 18" x 36" or 36" x 18" is the size for the duct opening measurement only, actual front end outer dimensions are approximately 19. 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