18" x 28" or 28" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Insulated Line + Product Details Size -

+ Product Details Size - 10"w X 32"h is the size for the duct opening measurement only

+ Product Details Size - 28"w X 20"h is the size for the duct opening measurement only

+ Product Details Size – 14" x 34" or 34" x 14" is the size for the duct opening measurement only

875" width X 22" height

+ Product Details Size – 28"w X 12"h is the size for the duct opening measurement only

18" x 28" or 28" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Insulated Line + Product Details Size -+ Product Details Perfect Fit & Easy Sizing Designed for a 18" x 28" OR 28" x 18" duct opening (measured at the opening), with actual outer dimensions of 20. 5" W x 30. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 17. 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