The Alside Promenade Sliding Glass Door series has 3 different styles to offer: Contemporary (3? Rail), Classic (5? Rail), and French (7? Rail). This series was created with Alside’s over 60 years of manufacturing innovation and excellence in mind. This series truly delivers all the must haves a sliding glass door should contain. The mainframe and sash are heavy-duty, the extrusions are multi-chambered and steel-reinforced interlocking meeting rails create increased durability and insulation. The Promenade series also features dual internal and external weather stripping and a 1? thick insulated glass unit for thermal efficiency.