6" x 36" or 36" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 38.5"] RG66 Black-HP + Product Details Size –

+ Product Details Size – 26"w X 20"h is the size for the duct opening measurement only

4" X 14" Is The Size For The Duct Opening (floor/vent hole) Measurement Only

Actual Filter Size – 29 3/4"w x 29 3/4" x 1"

with actual outer dimensions of 38

6" x 36" or 36" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 38.5"] RG66 Black-HP + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 6" x 36" or 36" x 6" duct opening (measured at the opening), with actual outer dimensions of 8. 5" W x 38. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 5. 75" x 35. 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