18" x 20" or 20" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Round Damper Ring Achieve the perfect airflow with

Achieve the perfect airflow with adjustable control by rotating the middle disk

These are built heavy duty for installation into brick and cement walls

or office environments

+ Product Details Size – 6" x 16" or 16" x 6" is the size for the duct opening measurement only

actual front end outer dimensions are approximately 20 5/8" width X 27 5/8" height -

18" x 20" or 20" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Round Damper Ring Achieve the perfect airflow with+ Product Details Perfect Fit & Easy Sizing Designed for a 18" x 20" OR 20" x 18" duct opening (measured at the opening), with actual outer dimensions of 20. 5" W x 22. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 17. 75" x 19. 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