6" x 28" or 28" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 30.5"] Aluminum + Product Details Size –

+ Product Details Size – 14" x 18" or 18" x 14" is the size for the duct opening measurement only

+ Product Details Size - 10"w X 10"h X 2"d (for duct opening measurement only)

actual front end outer dimensions are approximately 16 5/8" width X 10 5/8" height -

Actual Filter Size – 33 3/4"w x 21 3/4" x 1"

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

6" x 28" or 28" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 30.5"] Aluminum + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 6" x 28" or 28" x 6" duct opening (measured at the opening), with actual outer dimensions of 8. 5" W x 30. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 5. 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 Made