18" x 36" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Aluminum Actual Filter Size – 24

Actual Filter Size – 24 3/4"w x 5 3/4" x 1"

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

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

75" Width X 37

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

18" x 36" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Aluminum Actual Filter Size – 24+ 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