20" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Return Grille + Product Details Size -

+ Product Details Size - 26"w X 14"h is the size for the duct opening measurement only

+ Product Details Perfect Fit & Easy Sizing - Designed for a 6" x 18" or 18" x 6" duct opening (measured at the opening)

+ Product Details Perfect Fit & Easy Sizing - Designed for a 28" x 34" OR 34" x 28" duct opening (measured at the opening)

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

actual front end outer dimensions are approximately 16 5/8" width X 34 5/8" height

20" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Return Grille + Product Details Size -+ Product Details Perfect Fit & Easy Sizing Designed for a 20" x 18" OR 18" x 20" duct opening (measured at the opening), with actual outer dimensions of 22. 5" W x 20. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 19. 75" x 17. 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