8" x 18" or 18" x 8" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 10.5" X 20.5"] Grille Design – This airflow control

Design – This airflow control component are made to connect to a drop ceiling lay-in diffuser grille

6"w X 6"h 3-Way Fixed Curved Blade Air Supply Diffuser - Vent Duct Cover - Grille Register - Sidewall or Cieling - High Airflow - White

Actual Filter Size – 15 3/4"w x 24 3/4" x 1"

+ Product Details Size - 4"w X 28"h is the size for the duct opening measurement only

Installation is hassle-free

8" x 18" or 18" x 8" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 10.5" X 20.5"] Grille Design – This airflow control+ Product Details Perfect Fit & Easy Sizing Designed for a 8" x 18" or 18" x 8" duct opening (measured at the opening), with actual outer dimensions of 10. 5" W x 20. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 7. 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