At just 12.9 mm in thickness, the GSTB400 is the thinnest G-Steel that G-Shock has ever offered.

The GSTB400 collection arrives in three versions, two with bracelets and one with a black resin strap (shown). A Carbon Core Guard structure inner case and caseback provide strength while keeping the watch lightweight.

“In terms of design, the number of button guards has been reduced as much as possible, enabling the use of large stainless steel buttons that are slim yet easy to operate. The top bezel has been given five different finishes, while the middle bezel has been given four different finishes, which creates an elegant effect and changes the appearance of the texture of the metal depending on the viewing angle,” according to G-Shock.

The GSTB400’s slim case is made possible by the thinning of the parts that make up the inner module, without sacrificing any of its technical functions.

Technical features include automatic Bluetooth time and date syncing, solar power, 300-city world time, phone finder, dual time display, timer, 1/100th of a second stopwatch, 5 daily alarms, hand retract feature, and full auto-calendar. The G-Steel also has a 200-meter water-resistance rating and is highly shock resistant.

A redesigned dial with a vapor deposition treatment offers an enhanced metallic texture and elevates the look of the watch. A mineral crystal protects the dial.

The GSTB400-1A (shown) comes in a steel case with a resin strap for $320. The GSTB400D-1A comes in a stainless steel case with a matching bracelet for $400, and the GSTB400BD1A2 – comes in a black PVD stainless steel case with a matching bracelet for $500. All three references are available for pre-order starting May 12, 2021.