18" x 16" Cube Core Eggcrate Return Air Filter Grille for 1" Filter white + Product Details Size -

+ Product Details Size - 26"w X 28"h is the size for the duct opening measurement only

+ Product Details Size - 24"w X 18"h X 2"d (for duct opening measurement only)

Actual Filter Size – 25 3/4"w x 31 3/4" x 1"

Whether replacing an old register or installing a new vent

18" x 16" Cube Core Eggcrate Return Air Filter Grille for 1" Filter white + Product Details Size -+ Product Details Perfect Fit & Easy Sizing Designed for a 18" x 16" OR 16" X 18" duct opening (measured at the opening), with actual outer dimensions of 20. 5" W x 18. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 17. 75" x 15. 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