10" x 26" or 26" x 10" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 12.5" X 28.5"] Material_Steel the actual front end outer

the actual front end outer dimensions are 8" in diameter

Actual Filter Size – 31 3/4"w x 23 3/4" x 1"

the T-Bar vent covers

+ Product Details Size – 8" round duct opening

10" x 26" or 26" x 10" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 12.5" X 28.5"] Material_Steel the actual front end outer+ Product Details Perfect Fit & Easy Sizing Designed for a 10" x 26" or 26" x 10" duct opening (measured at the opening), with actual outer dimensions of 12. 5" W x 28. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 9. 75" x 25. 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