18" x 28" or 28" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Width_20in + Product Details Size –

+ Product Details Size – 26"w X 10"h is the size for the duct opening measurement only

+ Product Details Size – 10" X 2" is the size for the duct opening (floor/vent hole) measurement only

16" x 3" Aluminum Spiral Duct Air Vent Grille Cover - Fully Adjustable Double Deflection HVAC Air Supply

+ Product Spec Sheet Extruded Aluminum Ceiling Diffuser Spec Sheet

actual front end outer dimensions are approximately 26 5/8" width X 34 5/8" height

18" x 28" or 28" x 18" Cube Core Eggcrate Return Air Filter Grille for 1" Filter Width_20in + 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