28" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter d actual front end outer dimensions

actual front end outer dimensions are approximately 26 5/8" width X 28 5/8" height

actual front end outer dimensions are approximately 21

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

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

28" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter d actual front end outer dimensions+ 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