36" x 34" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Powder-Coated + Product Details Size -

+ Product Details Size - 20"w X 4"h is the size for the duct opening measurement only

+ Product Details Size – 20"w X 28"h is the size for the duct opening measurement only

All of these grills have dampers

actual front end outer dimensions are approximately 20 5/8" width X 16 5/8" height

36" x 34" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Powder-Coated + Product Details Size -+ Product Details Perfect Fit & Easy Sizing Designed for a 36" x 34" OR 34" x 36" duct opening (measured at the opening), with actual outer dimensions of 38. 5" W x 36. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 35. 75" x 35. 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