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

+ Product Details Size - 8" X 8" is the size for the duct opening measurement only

with actual front end outer dimensions of 5"

75" Width X 37

actual front end outer dimensions are approximately 41

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

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