28" x 20" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Compatible with Duct 6" + Product Details Perfect Fit

+ Product Details Perfect Fit & Easy Sizing - Designed for a 24" x 34" OR 34" x 24" duct opening (measured at the opening)

+ Product Details Perfect Fit & Easy Sizing - Designed for a 8" x 16" or 16" x 8" duct opening (measured at the opening)

4" X 12" Is The Size For The Duct Opening (floor/vent hole) Measurement Only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 28" x 18" OR 18" x 28" duct opening (measured at the opening)

+ Product Details Size - 26"w X 12"h is the size for the duct opening measurement only

28" x 20" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Compatible with Duct 6" + Product Details Perfect Fit+ 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