The Casio G-Shock GSTB400-1AWC sits in an interesting middle ground within G-Shock’s lineup — a full-metal G-Steel model that trades the line’s typical heft for a significantly slimmer profile, without sacrificing the ruggedness the brand is known for.

In his overview on aBlogtoWatch, Nick Lehner put the nail on the head by calling the GSTB400 series a “Goldilocks” G-Shock — premium enough to justify the price, practical enough to wear anywhere.
So it’s a genuine surprise to find it available right now at Costco for $230, or over $120 less than its retail price.
Thin, premium and capable

Where most G-Steel models lean into a blocky, oversized aesthetic, the GSTB400 takes a different approach. It’s built around G-Shock’s carbon core guard structure, which allows the resin-and-stainless-steel case to be slimmed down to just 12.9mm thick — making it one of the thinnest G-Steel models in the lineup when it launched and over a millimeter thinner than the GSTB100 series it replaced.
That slim package doesn’t come at the cost of capability. The GSTB400 retains Tough Solar charging, 200-meter water resistance, and Bluetooth connectivity via the G-Shock Connected app — which makes adjusting settings and syncing time zones far simpler than navigating the pushers alone.




