6" x 24" or 24" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 26.5"] w28h28 + Product Details Size –

+ Product Details Size – 26"w X 14"h is the size for the duct opening measurement only

Actual Filter Size – 33 3/4"w x 9 3/4" x 1"

and Diffusers

If your duct opening is 14 inches in diameter

+ Product Details Size - 32"w X 30"h is the size for the duct opening measurement only

6" x 24" or 24" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 26.5"] w28h28 + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 6" x 24" or 24" x 6" duct opening (measured at the opening), with actual outer dimensions of 8. 5" W x 26. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 5. 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 Made