The ST5500 adopts a design with an undercut in two or more areas to enhance usability from an ergonomic perspective. The undercut design is difficult to create with a single execution of the existing press process. “Hydroforming”, a way of shaping metals using high pressure hydraulic fluid, enables the design of complicated forms with an undercut based on a single process. “Hydroforming technology” has been specially improved and applied for the realization of this design concept. “Hydroforming technology” has enhanced the value of ST5500 by enabling environment-friendly manufacturing, based on reduction of energy and an ergonomic design.