18" x 24" Cube Core Eggcrate Return Air Filter Grille for 1" Filter White + Product Details Size -

+ Product Details Size - 8"w X 30"h is the size for the duct opening measurement only

The total outer size of this grille is the listed size plus 2

Actual Filter Size – 11 3/4"w x 11 3/4" x 1"

+ Product Details Size - 30"w X 2"h is the size for the duct opening measurement only

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18" x 24" Cube Core Eggcrate Return Air Filter Grille for 1" Filter White + Product Details Size -+ Product Details Perfect Fit & Easy Sizing Designed for a 18" x 24" OR 24" x 18" duct opening (measured at the opening), with actual outer dimensions of 20. 5" W x 26. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 17. 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