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

+ Product Details Size - 10"w X 24"h is the size for the duct opening measurement only

actual front end outer dimensions are approximately 26 5/8" width X 10 5/8" height

See our separate listing for Butterfly Dmaper to Control Airflow

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

actual front end outer dimensions are approximately 28 5/8" width X 18 5/8" height

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