30" x 28" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Round Damper Ring + Product Details Size –

+ Product Details Size – 40"w X 10"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 12" x 36" or 36" x 12" duct opening (measured at the opening)

+ Product Details Size – 8" x 24" or 24" x 8" is the size for the duct opening measurement only

+ Product Details Size - 8"w X 36"h is the size for the duct opening measurement only

30" x 28" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Round Damper Ring + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 30" x 28" OR 28" x 30" duct opening (measured at the opening), with actual outer dimensions of 32. 5" W x 30. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 29. 75" x 27. 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