Material use by DUN, Gunmetal was developed by TOYOTA Central Research & Development Laboratories.Inc.,which is the think-tank of Toyota group, and is one of Titan alloy like rubber in terms of properties thought is metallic material. Its very sensitive and flexible but stronger and tougher. Further, this alloy never becomes hardened how heavily deformed at room temperature or below. That is , its cold-work-ability is unlimited. This alloy is far less likely to corrode and more friendly to the human body compared with ordinary Titanium alloy.