16"W X 16"H [Duct Opening] 4-Way Aluminum Curved Blade Adjustable Air Supply HVAC Diffuser [Outer Dimensions: 17.75"W X 17.75"H] Compatible With Duct 10in + Product Details Size -

+ Product Details Size - 8"w X 30"h is the size for the duct opening measurement only

And The Cooler Air From Outside WIll Flow In From The Bottom

+ Product Details Size - 20"w X 6"h is the size for the duct opening measurement only

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16"W X 16"H [Duct Opening] 4-Way Aluminum Curved Blade Adjustable Air Supply HVAC Diffuser [Outer Dimensions: 17.75"W X 17.75"H] Compatible With Duct 10in + Product Details Size -+ Product Details Size 16"w X 16"h is the size for the duct opening measurement only, actual front end outer dimensions are 17. 75" width X 17. 75" height. Design Individually adjusting curved blades for better air flow control. Screws Included High Quality Aluminum The premium durable aluminum will never rust and it will never wear through leaving the material with an elegant, beautiful, and smooth surface, adds a luxurious touch to any home.