18" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Grille + Product Details Size –

+ Product Details Size – 8" x 12" or 12" x 8" is the size for the duct opening measurement only

+ Product Details Size - 36"w X 20"h is the size for the duct opening measurement only

Designed for both wall and ceiling applications

+ Product Details Size - 25"w X 20"h is the size for the duct opening measurement only

18" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Grille + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 18" x 18" duct opening (measured at the opening), with actual outer dimensions of 20. 5" W x 20. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 20. 75" x 20. 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 Made from