18" x 26" or 26" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Compatible With Duct 12in + Product Details Perfect Fit

+ Product Details Perfect Fit & Easy Sizing - Designed for a 14" x 14" duct opening (measured at the opening)

With a 8" diameter for the duct opening measurement

then you'll need a 14-inch round vent

actual front end outer dimensions are approximately 32 5/8" width X 8 5/8" height -

easy unrestricted airflow

18" x 26" or 26" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Compatible With Duct 12in + Product Details Perfect Fit+ Product Details Perfect Fit & Easy Sizing Designed for a 18" x 26" OR 26" x 18" duct opening (measured at the opening), with actual outer dimensions of 20. 5" W x 28. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 17. 75" x 27. 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