18" x 20" or 20" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Material_Steel and smooth surface

and smooth surface

Designed with a ring base for flexible installation

Refrigerant - 1/2" White Insulation - 50' Long

durable plastic

18" x 20" or 20" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Material_Steel and smooth surface+ 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