Introducing new color variations to the lineup of slim G-STEEL GST-B400 models with new, improved designs made possible by a thin module and carbon core guard structure. The GST-B400BD features a black IP case and band, and a blue vapor deposition dial.The GST-B400 is made possible by even further miniaturization of its parts and thinning of its modules without sacrificing any Bluetooth or solar function. Power consumption has also been significantly reduced.In addition, the carbon core guard structure of this model helps to make it the thinnest of the G-STEEL Series (as of Apr 2021) while maintaining a high level of impact resistance. The thickness from the back cover to the bezel top is only 12.9 mm, which is more than one millimeter less than the GST-B100 model.