Aluminum screws and titanium ball ends reduce the weight of the upper part of the chassis and promote weight reduction and a low center of gravity. All of them are high-precision parts manufactured by shaving, and are excellent products that improve the quality of machine make-up. In particular, the aluminum screws that secure the upper deck and bulkhead cap not only achieve a significant weight reduction, but also affect the driving characteristics, making it possible to create a supple feel.