36" x 30" Cube Core Eggcrate Return Air Filter Grille for 1" Filter w10h10 + Product Details Size –

+ Product Details Size – 25"w X 28"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 12" x 24" or 24" x 12" duct opening (measured at the opening)

+ Product Details Size - The listed 12" diameter refers specifically to the size of the duct opening

and Diffusers

with actual outer dimensions of 28

36" x 30" Cube Core Eggcrate Return Air Filter Grille for 1" Filter w10h10 + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 36" x 30" OR 30" x 36" duct opening (measured at the opening), with actual outer dimensions of 38. 5" W x 32. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 35. 75" x 29. 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