6" x 36" or 36" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 38.5"] white + Product Details Size –

+ Product Details Size – 16"w X 12"h is the size for the duct opening measurement only

+ Product Details Size – 18" x 26" or 26" x 18" is the size for the duct opening measurement only

We carry sizes the big box stores don't

+ Product Details Perfect Fit & Easy Sizing - Designed for a 18" x 28" OR 28" x 18" duct opening (measured at the opening)

Actual Filter Size – 24 3/4"w x 29 3/4" x 1"

6" x 36" or 36" x 6" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 8.5" X 38.5"] white + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 6" x 36" or 36" x 6" duct opening (measured at the opening), with actual outer dimensions of 8. 5" W x 38. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 5. 75" x 35. 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