28" x 20" Cube Core Eggcrate Return Air Filter Grille for 1" Filter ceiling + Product Details Size -

+ Product Details Size - 30"w X 2"h is the size for the duct opening measurement only

ISO Supply Diffusers perform efficiently with air loadings of 6 to 30 air changes per hour (based on 10 ft

Actual Filter Size – 31 3/4"w x 35 3/4" x 1"

+ Product Details Size - 10"w X 6"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 10" x 30" or 30" x 10" duct opening (measured at the opening)

28" x 20" Cube Core Eggcrate Return Air Filter Grille for 1" Filter ceiling + Product Details Size -+ 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