12" x 18" or 18" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 14.5" X 20.5"] 10in diameter + Product Details Size –

+ Product Details Size – 34" x 34" is the size for the duct opening measurement only

+ Product Details Size - 8"w X 6"h is the size for the duct opening measurement only

The first number in a grille size represents the width

Tamper-Proof Security – Features a robust design to prevent unauthorized access and protect your thermostat settings

When it's time to upgrade your HVAC Vents in your house

12" x 18" or 18" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 14.5" X 20.5"] 10in diameter + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 12" x 18" or 18" x 12" duct opening (measured at the opening), with actual outer dimensions of 14. 5" W x 20. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 11. 75" x 17. 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