18" x 36" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Aluminum + Product Details Perfect Fit

+ Product Details Perfect Fit & Easy Sizing - Designed for a 8" x 26" or 26" x 8" duct opening (measured at the opening)

+ Product Details Perfect Fit & Easy Sizing - Designed for a 6" x 32" or 32" x 6" duct opening (measured at the opening)

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

Ideal for Walls & Ceilings: Designed for seamless installation in standard 12" X 4" duct openings

75" Width X 37

18" x 36" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Aluminum + Product Details Perfect Fit+ Product Details Perfect Fit & Easy Sizing Designed for a 18" x 36" OR 36" x 18" duct opening (measured at the opening), with actual outer dimensions of 20. 5" W x 38. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 17. 75" x 35. 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