12" x 8" or 8" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 14.5" X 10.5"] Powder Coated + Product Details Size –

+ Product Details Size – 36"w X 18"h is the size for the duct opening measurement only

+ Product Details Size – 8"w X 24"h is the size for the duct opening measurement only

Actual Filter Size – 9 3/4"w x 33 3/4" x 1"

+ Product Details Size – 20" x 26 or 26" x 20" is the size for the duct opening measurement only

Actual Front End Outer Dimensions Are 7

12" x 8" or 8" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter - Aluminum - White [Outer Dimensions: 14.5" X 10.5"] Powder Coated + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 12" x 8" or 8" x 12" duct opening (measured at the opening), with actual outer dimensions of 14. 5" W x 10. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 11. 75" x 7. 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