12" x 16" or 16" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 14.5" X 18.5"] 10" Diameter + Product Details Size -

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

with actual outer dimensions of 10

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

+ Product Details Size – 16" x 18" or 18" x 16" is the size for the duct opening measurement only

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

12" x 16" or 16" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 14.5" X 18.5"] 10" Diameter + Product Details Size -+ Product Details Perfect Fit & Easy Sizing Designed for a 12" x 16" or 16" x 12" duct opening (measured at the opening), with actual outer dimensions of 14. 5" W x 18. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 11. 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