10" x 24" or 24" x 10" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 12.5" X 26.5"] 12" Diameter + Product Details Size -

+ Product Details Size - 20"w X 18"h is the size for the duct opening measurement only

Efficient Airflow Design: The slots are meticulously angled to diversify airflow in two directions

Solid Base for Stability – Built with a solid base for reliable mounting and stability

+ Product Details Size - 8"w X 12"h is the size for the duct opening measurement only

10" x 24" or 24" x 10" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 12.5" X 26.5"] 12" Diameter + Product Details Size -+ Product Details Perfect Fit & Easy Sizing Designed for a 10" x 24" or 24" x 10" duct opening (measured at the opening), with actual outer dimensions of 12. 5" W x 26. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 9. 75" x 23. 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