28" x 20" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Color_White + Product Details Outer dimensions:

+ Product Details Outer dimensions: 31

+ Product Details Perfect Fit & Easy Sizing - Designed for a 28" x 36" OR 36" x 28" duct opening (measured at the opening)

+ Product Details Size - 34"w X 12"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 16" x 36" OR 36" X 16" duct opening (measured at the opening)

28" x 20" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Color_White + Product Details Outer dimensions:+ Product Details Perfect Fit & Easy Sizing Designed for a 28" x 20" OR 20" x 28" duct opening (measured at the opening), with actual outer dimensions of 30. 5" W x 22. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 27. 75" x 19. 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