28" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 18" Diameter + Product Details Outer dimensions:

+ Product Details Outer dimensions: 21

8" Diameter Is The Size For The Duct Opening Measurement Only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 6" x 28" or 28" x 6" duct opening (measured at the opening)

Center Core is Removable for Easy Access and Maintence

28" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 18" Diameter + Product Details Outer dimensions:+ Product Details Perfect Fit & Easy Sizing Designed for a 28" x 6" OR 6" x 28" duct opening (measured at the opening), with actual outer dimensions of 30. 5" W x 8. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 27. 75" x 5. 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