18" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 8in diameter + Product Details Perfect Fit

+ Product Details Perfect Fit & Easy Sizing - Designed for a 16" x 16" duct opening (measured at the opening)

+ Product Details Size - 3" Diameter is the size for the duct opening measurement only

+ Product Details Size – 28" x 28" is the size for the duct opening measurement only

high-impact plastic to provide reliable and long-lasting protection for your thermostat

Actual Filter Size – 27 3/4"w x 35 3/4" x 1"

18" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 8in diameter + Product Details Perfect Fit+ Product Details Perfect Fit & Easy Sizing Designed for a 18" x 6" OR 6" X 18" duct opening (measured at the opening), with actual outer dimensions of 20. 5" W x 8. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 17. 75" x 5. 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