16" x 32" or 32" x 16" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 18" Diameter only measure the "hole" in

only measure the "hole" in the wall/duct

+ Product Details Size - 28"w X 18"h is the size for the duct opening measurement only

Quality Packaging – carefully shrink wrapped with cardboard backing to prevent damage in shipment

It comes with two versatile mounting base options—solid and ring—making installation simple and flexible

All of these grills have dampers

16" x 32" or 32" x 16" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 18" Diameter only measure the "hole" in+ Product Details Perfect Fit & Easy Sizing Designed for a 16" x 32" OR 32" X 16" duct opening (measured at the opening), with actual outer dimensions of 18. 5" W x 34. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 15. 75" x 31. 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