10"W X 8"H [Duct Opening] Never Rust Plastic 3-Way-Vertical Air Supply Register - HVAC Vent Duct Grille - Off White [Outer Dimensions: 11.75"W X 9.75"H] 10in diameter Ideal for Walls & Ceilings:

Ideal for Walls & Ceilings: Designed for seamless installation in standard 20" X 20" duct openings

the gap will expand and retract to meet perfect air supply needed

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The total outer size of this grille is the listed size plus 3"

[Outer Dimensions: 38

10"W X 8"H [Duct Opening] Never Rust Plastic 3-Way-Vertical Air Supply Register - HVAC Vent Duct Grille - Off White [Outer Dimensions: 11.75"W X 9.75"H] 10in diameter Ideal for Walls & Ceilings:+ Product Details Size 10"w X 8"h is the size for the duct opening measurement only, actual front end outer dimensions are approximately 11. 75" width X 9. 75" height. Design Rigid gauge ABS plastic. Rigid gauge built for durability and long life in mind, but still light and handy. Powder coat finish. Smooth, scratch resistant, beautiful. Looks like new after years of use. Screws Included High Quality High quality ABS plastic will never rust, no sharp