The Velux CO4 GGL/GGU (Size 55cm wide x 98cm long)centre-pivot window with it's comfortable control bar located at the top of the window. This window has two finishes, (GGL)varnished natural pine and (GGU)White polyurethane(EVERFINISH QUALITY). The VELUX roof window has proved itself over many years. If you are looking for a centre-pivot window, you should choose the VELUX GGL/GGU centre-pivot roof window.