10" x 36" or 36" x 10" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 12.5" X 38.5"] Powder-Coated + Product Details Size –

+ Product Details Size – 16"w X 6"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 22 5/8" width X 16 5/8" height

The first number in a grille size represents the width

+ Product Details Size - 6"w X 4"h is the size for the duct opening measurement only

+ Product Details Size – 36"w X 6"h is the size for the duct opening measurement only

10" x 36" or 36" x 10" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 12.5" X 38.5"] Powder-Coated + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 10" x 36" or 36" x 10" duct opening (measured at the opening), with actual outer dimensions of 12. 5" W x 38. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 9. 75" x 35. 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