28" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter d + Product Details Size –

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

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

designed to distribute air evenly throughout your space

8" Diameter Is The Size For The Duct Opening Measurement Only

+ Product Details Size - 12"w X 30"h X 2"d (for duct opening measurement only)

28" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter d + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 28" x 18" OR 18" x 28" duct opening (measured at the opening), with actual outer dimensions of 30. 5" W x 20. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 27. 75" x 17. 75" x 1" Premium Airflow Efficiency High performance cube core eggcrate design allows 95% airflow efficiency, reducing energy costs and maximizing HVAC system lifespan. Durable, Rust Free Aluminum