28" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Supply Grille + Product Details Size -

+ Product Details Size - 4"w X 32"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 28 5/8" width X 20 5/8" height

+ Product Details Size – 14"w X 12"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 18" x 26" OR 26" x 18" duct opening (measured at the opening)

+ Product Details Perfect Fit & Easy Sizing - Designed for a 8" x 34" or 34" x 8" duct opening (measured at the opening)

28" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Supply Grille + Product Details Size -+ Product Details Perfect Fit & Easy Sizing Designed for a 28" x 6" OR 6" x 28" duct opening (measured at the opening), with actual outer dimensions of 30. 5" W x 8. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 27. 75" x 5. 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 Made