18" x 20" or 20" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter sidewall + Product Details High Quality

+ Product Details High Quality - Aluminum housing on the outside and on the inside for the best insulation value

+ Product Details Size – 28"w X 34"h is the size for the duct opening measurement only

875" width X 9

+ Product Details Size - 4"w X 34"h is the size for the duct opening measurement only

18" x 20" or 20" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter sidewall + Product Details High Quality+ 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