8" x 10" or 10" x 8" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 10.5" X 12.5"] 6" Diameter /* Darker color for better

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+ Product Details Size – 18" x 34" or 34" x 18" is the size for the duct opening measurement only

actual front end outer dimensions are approximately 36 5/8" width X 16 5/8" height

Actual Filter Size – 13 3/4"w x 5 3/4" x 1"

This versatile diffuser is available in 1-way

8" x 10" or 10" x 8" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 10.5" X 12.5"] 6" Diameter /* Darker color for better+ Product Details Perfect Fit & Easy Sizing Designed for a 8" x 10" or 10" x 8" duct opening (measured at the opening), with actual outer dimensions of 10. 5" W x 12. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 7. 75" x 9. 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