18" x 30" or 30" x 18" Cube Core Eggcrate Return Air Grille 10" Diameter the gap will expand and

the gap will expand and retract to meet perfect air supply needed

actual front end outer dimensions are approximately 20 5/8" width X 10 5/8" height

you can watch this informative video tutorial: How to Measure Your Vent Hole Before Ordering a Grille

Designed for optimal airflow and lasting durability

Customize effortlessly with a removable face/door

18" x 30" or 30" x 18" Cube Core Eggcrate Return Air Grille 10" Diameter the gap will expand and+ Product Details Size 18" x 30" or 30" x 18" is the size for the duct opening measurement only, actual front end outer dimensions are approximately 19. 75" X 31. 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