36" x 26" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 14in diameter actual front end outer dimensions

actual front end outer dimensions are approximately 27 5/8" width X 28 5/8" height

+ Product Details Size - 20"w X 2"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 18" x 20" OR 20" x 18" duct opening (measured at the opening)

This versatile diffuser is available in 1-way

36" x 26" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 14in diameter actual front end outer dimensions+ Product Details Perfect Fit & Easy Sizing Designed for a 36" x 26" OR 26" x 36" duct opening (measured at the opening), with actual outer dimensions of 38. 5" W x 28. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 35. 75" x 25. 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