24" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Return actual front end outer dimensions

actual front end outer dimensions are approximately 12 5/8" width X 24 5/8" height

Actual Filter Size – 27 3/4"w x 33 3/4" x 1"

+ Product Details Size - 28"w X 12"h is the size for the duct opening measurement only

If you are looking to enhance your project with a top-of-the-line unit

+ Product Details Size – 30"w X 36"h is the size for the duct opening measurement only

24" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Return actual front end outer dimensions+ Product Details Perfect Fit & Easy Sizing Designed for a 24" x 18" OR 18" x 24" duct opening (measured at the opening), with actual outer dimensions of 26. 5" W x 20. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 23. 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