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

+ Product Details Size – 24"w X 26"h is the size for the duct opening measurement only

And One Towards The Bottom Of The Door

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

Universal Fit – Measures 6" wide x 3-1-13/16" high x 3-1/8" deep

+ Product Details Size - 34"w X 20"h is the size for the duct opening measurement only

36" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Return + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 36" x 18" OR 18" x 36" duct opening (measured at the opening), with actual outer dimensions of 38. 5" W x 20. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 35. 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