Bri-Rus Skylight Dome. Skylights are made of high performance thermoformed polycarbonate to be long lasting and easy to clean. When choosing a Skylight, measure your rough hole opening as well as the overall exterior size. There is a size to replace most manufacturer original equipment. Skylights sit directly on your RV roof. If necessary, an inner garnish is available to finish the inside hole (order separately). No metal flange is used with these single pane skylights. Use a skylight size that is equal to or greater than your hole dimensions. Note: inners must be the exact size as the hole you are working with. 63902 is a Rectangular Skylight only, Smoke color. Hole size 21in x 62in flange size 25.25in x 66.5in height 4in, and does not have screw holes (glue-down model).