The advantage of aluminum ?windows is that all the aluminum materials above 1.4 are added with a heat insulation layer. It also has good sound insulation, heat insulation, fire prevention, air tightness, water tightness, corrosion resistance, insulation, maintenance-free, etc. It is a metal aluminum profile that can be used for a long time without changing the shape and color. https://www.builtecwindow.com/al...liding-glass-window.html