18" x 20" or 20" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Material_Steel + Product Details Size -

+ Product Details Size - 22"w X 4"h is the size for the duct opening measurement only

+ Product Details Size - 24"w X 10"h is the size for the duct opening measurement only

Designed with a ring base for flexible installation

Actual Filter Size – 35 3/4"w x 25 3/4" x 1"

and smooth surface

18" x 20" or 20" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Material_Steel + Product Details Size -+ 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