18" x 36" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Aluminum with actual front end outer

with actual front end outer dimensions of 5"

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

actual front end outer dimensions are approximately 24 5/8" width X 20 5/8" height

Ideal for Walls & Ceilings: Designed for seamless installation in standard 12" X 4" duct openings

Actual Filter Size – 15 3/4"w x 15 3/4" x 1"

18" x 36" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Aluminum with actual front end outer+ Product Details Perfect Fit & Easy Sizing Designed for a 18" x 36" OR 36" x 18" duct opening (measured at the opening), with actual outer dimensions of 20. 5" W x 38. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 17. 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