12" x 28" or 28" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter flat stamped steel + Product Details Size –

+ Product Details Size – 16" x 18" or 18" x 16" is the size for the duct opening measurement only

Great emphasis has been invested in the design of this product to prevent it from kinking in sharp bends & turns and to hold steady and at full diameter in all applications

+ Product Details Perfect Fit & Easy Sizing - Designed for a 12" x 18" or 18" x 12" duct opening (measured at the opening)

Adjustable airflow control – Adjustable airflow control: The system allows users to customize the amount of air supply

+ Product Details Size – 16" x 16" is the size for the duct opening measurement only

12" x 28" or 28" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter flat stamped steel + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 12" x 28" or 28" x 12" duct opening (measured at the opening), with actual outer dimensions of 14. 5" W x 30. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 11. 75" x 27. 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