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

+ Product Details Size - 24"w X 30"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 18" x 12" OR 12" X 18" duct opening (measured at the opening)

providing efficient performance of up to 300m3/h

+ Product Details Size – 25"w X 18"h is the size for the duct opening measurement only

+ Product Details Size – 20"w X 10"h is the size for the duct opening measurement only

28" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Aluminum - Cube Core + 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