6" x 12" or 6" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 14.5"] Color_R-4.2 Yellow Actual Filter Size – 21

Actual Filter Size – 21 3/4"w x 27 3/4" x 1"

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Ideal for Walls & Ceilings: Designed for seamless installation in standard 18" X 6" duct openings

+ Product Details Perfect Fit & Easy Sizing - Designed for a 12" x 20" or 20" x 12" duct opening (measured at the opening)

6" x 12" or 6" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 14.5"] Color_R-4.2 Yellow Actual Filter Size – 21+ Product Details Perfect Fit & Easy Sizing Designed for a 6" x 12" or 12" x 6" duct opening (measured at the opening), with actual outer dimensions of 8. 5" W x 14. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 5. 75" x 11. 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 Made