The 350S Commercial/Industrial insulated steel garage doors (formerly marketed as the Therma Series 308 and 650) are rugged and beautiful. They are designed to have a sleek and appealing appearance with great weather resistance. Our 350S doors are made with a sandwich type construction, steel outer skins are formed and then pressure bonded to a polystyrene core giving the door maximum strength, a natural thermal break, and superior insulating efficiencies with an R-value of 10.4.