Casio's metal CasiOak lineup has split into several distinct models over the years, each one trading off a different combination of features. The GM-2100 offers a pure metal case without connectivity; the resin GA-B2100 adds solar charging and Bluetooth but skips the steel. The GBM-2100 was built to close that gap — a forged stainless steel bezel over a resin case, paired with both Tough Solar charging and Bluetooth smartphone link, incorporating two of the most requested features in the modern G-Shock catalog into a single watch.
A lightweight, eco-friendly biomass resin band keeps the overall weight manageable despite the metal bezel, while 200m water resistance and Casio's standard shock-resistant construction carry over from the rest of the 2100 series. It sits as a genuine middle ground in Casio's octagonal lineup — more capable than the plain metal GM-2100, more durable-feeling than the all-resin GA-B2100 — for buyers who don't want to choose between materials and features.
