G-SHOCK introduces a new color variation from the G-STEEL GST-B400, with a new slim configuration made possible by its thin module and carbon core guard structure. The bezel has a new green ion-plated (IP) finish, which brings out the texture of the metal. The design of the watch also comprises of large and minimalistic stainless-steel buttons, making it easy to operate. The top bezel has five different finishes, while the middle bezel has four different finishes, which creates an elegant effect and changes the appearance of the texture of the metal depending on the viewing angle.

In terms of functions, the GST-B400 has Bluetooth® and solar features, despite its thin build. This is made possible by miniaturization in components and thinning of its modules. Moreover, this series’ power consumption has also been significantly reduced.