32" x 28" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 10" Diameter + Product Details Size –

+ Product Details Size – 20" x 28" or 28" x 20" is the size for the duct opening measurement only

then you'll need a 14-inch round vent

+ Product Details Size – 36"w X 32"h is the size for the duct opening measurement only

+ Product Details Outer dimensions: – fits a duct opening

Design – This airflow control component are made to connect to a drop ceiling lay-in diffuser grille

32" x 28" Cube Core Eggcrate Return Air Filter Grille for 1" Filter 10" Diameter + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 32" x 28" OR 28" x 32" duct opening (measured at the opening), with actual outer dimensions of 34. 5" W x 30. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 31. 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