18" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 14in diameter + Product Details Size -

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

+ Product Details Perfect Fit & Easy Sizing - Designed for a 18" x 12" OR 12" X 18" duct opening (measured at the opening)

Gymnasiums & Restaurants

actual front end outer dimensions are approximately 18 5/8" width X 12 5/8" height

+ Product Details Perfect Fit & Easy Sizing - Designed for a 24" x 24" duct opening (measured at the opening)

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