26" x 20" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 14" Diameter + Product Details Size -

+ Product Details Size - 20"w X 10"h is the size for the duct opening measurement only

The 1/2" white insulation

+ Product Details Perfect Fit & Easy Sizing - Designed for a 22" x 32" OR 32" x 22" duct opening (measured at the opening)

Actual Filter Size – 11 3/4"w x 11 3/4" x 1"

+ Product Details Size - The listed 4" diameter refers specifically to the size of the duct opening

26" x 20" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 14" Diameter + Product Details Size -+ Product Details Perfect Fit & Easy Sizing Designed for a 26" x 20" OR 20" x 26" duct opening (measured at the opening), with actual outer dimensions of 28. 5" W x 22. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 25. 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