10" x 36" or 36" x 10" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 12.5" X 38.5"] Supply Grille + Product Details Size –

+ Product Details Size – 25"w X 18"h is the size for the duct opening measurement only

Adjustable airflow control - by rotating the middle disk

Ideal for Walls & Ceilings: Designed for seamless installation in standard 18" X 8" duct openings

this diffuser is the perfect blend of function and style for your home

With a 5" diameter for the duct opening measurement

10" x 36" or 36" x 10" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 12.5" X 38.5"] Supply Grille + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 10" x 36" or 36" x 10" duct opening (measured at the opening), with actual outer dimensions of 12. 5" W x 38. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 9. 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