Builders Edge 120011818069 Vent, Tan The Builders Edge 18" Octagon (Net free venting area: 26 sq in	) provides added architectural detail with their wood grain finish and sharp distinctive characteristics Installation is easy with our wide nailing flange, leveling lines, and adjustable stop gauge Our patented snap-on trim ring hides rough cuts and reduces installation time, while providing a finished appearance once the vent has been installed