18" x 28" or 28" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Fixed Blades + Product Details Size –

+ Product Details Size – 12" X 4" is the size for the duct opening (floor/vent hole) measurement only

ensuring even air distribution throughout your space

but still light and handy

actual front end outer dimensions are approximately 30 5/8" width X 26 5/8" height

18" x 28" or 28" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Fixed Blades + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 18" x 28" OR 28" x 18" duct opening (measured at the opening), with actual outer dimensions of 20. 5" W x 30. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 17. 75" x 27. 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