From G-Shock, the watch that has always strived for toughness, the first G-Steel lineup models to offer chronograph performance in analog format. Thought all the dials on these models are analog, they still boast G-Shock level shock resistance. Rotation of the blades reveals the red color behind the disc, and this change in color is used to indicate battery level and the alarm on/off setting. The blades also rotate in timekeeping and stopwatch modes as time passes. A new layer guard structure consists of resin cushioning parts inside the case, for a more elegant design and better fit to the wrist. High-density mounting technology makes it possible to create a module that is smaller and thinner, which also contributes to a better fit. These watches are equipped with Bluetooth that allows them to connect to a smartphone at the press of a button, And get time information from internet time server. Other functions include tough solar in conjunction with CASIO original power saving technology for a stable supply of power, highbrightness LED light illumination, and dual dial world time. The GST-B100D comes with a simple stainless steel band, while the GST-B100 has a solid case and urethane band.