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 manufacturers' 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. Skylights include care instructions and include a tube of approved urethane sealant that must be used when installing.