The case holds the movement, protecting it from the elements and wear and tear. The case is available in many shapes, including round, square, oval, rectangular, tank, carre, carage, tonneau and asymmetrical. It can be made from different metals, including platinum, 18K gold, 14K gold, gold plate, stainless steel, titanium, ceramic, tantalum, tungsten carbide, PVD or diamond-like carbon.