G-Shock Watch G-Steel GST-B300SD-1AER. The GST B300SD 1AER, the latest addition to the G STEEL line of G SHOCK shock resistant watches. The GST B300 series is the first G STEEL watch with a front button, which adopts a new Carbon Core Guard structure that delivers superior shock resistance by leveraging the lightness and outstanding rigidity of carbon fiber. The battery indicator at the 6 oÕclock position, designed to evoke a brake disk, shows the remaining battery power by an arrow pointer and a curved red bar, providing visually interesting ways to check the battery. As for functions, in addition to automatic time adjustment via Bluetooth when paired with a dedicated smartphone app, the watch features world time setting for over 300 cities as well as various alarm and countdowin timer settings, all easy to use. It is also equipped with other practical functions such as the Tough Solar, solar charging system developed by Casio, and a high luminosity full auto double LED light.