28" x 20" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Compatible with Duct 6" Ideal for Walls & Ceilings:

Ideal for Walls & Ceilings: Designed for seamless installation in standard 18" X 10" duct openings

+ Product Details Size - 12"w X 28"h is the size for the duct opening measurement only

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

designed to distribute air evenly throughout your space

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

28" x 20" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Compatible with Duct 6" Ideal for Walls & Ceilings:+ 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