22.50" x 22.50" Rough Opening Aluminum Curb Mount Double Dome Skylight (Mounting Flange 26 1/4"x 26 1/4")Rough Opening: 22 1 2 x 22 1 2 Outside Wood Curb Dimension: 25 1 2 x 25 1 2 Mounting Flange Dimension: 26 1 4 x 26 1 4 To view diagram of these dimensions click on image in upper left corner next to pictures of skylights. All Polycarbonate units are made with a clear acrylic inner dome (only concerned about impact protection on outside of skylight) Our curb mount skylight comes with fully integrated frame and built in condensation system. NO RETURNS