thermal break material made the door frame and double insulated glass manufacture.The TP68 folding sliding door design can maximized the room space when full opening, also can open small space when needed. It is a wise choice for door option. The Thermally Controlled system is the result of an extensive design process focused on energy efficiency, structural integrity and versatility featuring a narrow 2 15/16" stile and rail profile with thermal breaks throughout for improved performance. Our proprietary core and fascia design allows for split finish color options for the interior and exterior providing maximum design flexibility. Perfect for those climates where you want to keep either the cold or hot air out and the ideal temperature in. The Aluminum Thermally Controlled system offers the sleek and contemporary design of our Aluminum system with improved thermal performance and added features.