G-Shock Watch Octagonal GM-S2100 Unisex GM-S2100-3AER. Building on the iconic 2100 octagonal shape is the new GM-S2100 series, which are slim mid-sized G-SHOCKs with a simple yet bold design. Only the lettering at the top and bottom are engraved, for a stylish edge, and the dial, flattened for slimness, is treated with ion plating colour and mirrored indexes to add depth and tone. Still 200M water resistant with functions such as World Time, Stopwatch and a Timer.