6" x 16" or 16" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 18.5"] Adjustable Return only measure the "hole" in

only measure the "hole" in the wall/duct

Actual Filter Size – 17 3/4"w x 27 3/4" x 1"

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

+ Product Details Size - 8"w X 30"h is the size for the duct opening measurement only

6" x 16" or 16" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 18.5"] Adjustable Return only measure the "hole" in+ Product Details Perfect Fit & Easy Sizing Designed for a 6" x 16" or 16" x 6" duct opening (measured at the opening), with actual outer dimensions of 8. 5" W x 18. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 5. 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 Made