26" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter return grille + Product Details Size –

+ Product Details Size – 12"w X 20"h is the size for the duct opening measurement only

+ Product Details Size - 8"w X 6"h is the size for the duct opening measurement only

For 8" Round Duct Opening - Spiral or Flex

Adjust the airflow to your preference by simply opening or closing the top panel

actual front end outer dimensions are 21

26" x 12" Cube Core Eggcrate Return Air Filter Grille for 1" Filter return grille + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 26" x 12" OR 12" x 26" duct opening (measured at the opening), with actual outer dimensions of 28. 5" W x 14. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 25. 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