28" x 36" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Floor Grille + Product Details Size –

+ Product Details Size – 28"w X 18"h is the size for the duct opening measurement only

See our separate listing for Butterfly Dmaper to Control Airflow

Quality Packaging - Carefully Shrink Wrapped with Cardboard Backing to Prevent Damage in Shipment

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+ Product Details Size – 2"w X 12"h is the size for the duct opening measurement only

28" x 36" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Floor Grille + Product Details Size –+ Product Details Perfect Fit & Easy Sizing Designed for a 28" x 36" OR 36" x 28" duct opening (measured at the opening), with actual outer dimensions of 30. 5" W x 38. 5" H. Please check the measuring guide to ensure a proper fit. Filter Size 27. 75" x 35. 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