36" x 28" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 3-Way or 4-Way + Product Details Size –

+ Product Details Size – 20"w X 6"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 6" x 8" or 8" x 6" duct opening (measured at the opening)

actual front end outer dimensions are approximately 22 5/8" width X 26 5/8" height

+ Product Details Perfect Fit & Easy Sizing - Designed for a 10" x 14" or 14" x 10" duct opening (measured at the opening)

+ Product Details Perfect Fit & Easy Sizing - Designed for a 26" x 36" OR 36" x 26" duct opening (measured at the opening)

36" x 28" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 3-Way or 4-Way + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 36" x 28" OR 28" x 36" duct opening (measured at the opening), with actual outer dimensions of 38. 5" W x 30. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 35. 75" x 27. 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