30" x 30" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Compatible With Duct 12in actual front end outer dimensions

actual front end outer dimensions are approximately 16 5/8" width X 18 5/8" height

For 14" Round Duct Opening - Spiral or Flex

actual front end outer dimensions are approximately 32 5/8" width X 28 5/8" height

or commercial environment

30" x 30" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Compatible With Duct 12in actual front end outer dimensions+ Product Details Perfect Fit & Easy Sizing Designed for a 30" x 30" duct opening (measured at the opening), with actual outer dimensions of 32. 5" W x 32. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 29. 75" x 29. 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 from