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

+ Product Details Size – 16" x 18" or 18" x 16" is the size for the duct opening measurement only

actual front end outer dimensions are approximately 30 5/8" width X 38 5/8" height

Actual Filter Size – 25 3/4"w x 7 3/4" x 1"

Actual Filter Size – 23 3/4"w x 33 3/4" x 1"

Measure the size of the air duct/drywall opening

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