The G-Shock GSTB400-1A redefines durability and style with an ultra-slim carbon core guard structure, making it the thinnest G-STEEL model yet. Measuring just 12.9mm thick, it combines a silver stainless-steel and resin case, black dial with silver accents, and a black resin strap for a bold yet refined look. Despite its slim build, it remains incredibly tough—shock resistant, 200m water resistant, and powered by Tough Solar technology for long-lasting performance. The Bluetooth® connectivity allows smartphone linking for auto time adjustment, phone finder, and access to around 300 world time cities. Key features include dual time display, stopwatch, alarm, Super Illuminator LED light, and a full auto-calendar (to 2099). With energy-saving mode, battery level indicator, and up to 24 months of operation in power-save mode, the GSTB400-1A combines cutting-edge functionality with a sleek, modern design built for any occasion. - Case Size: 58.1 × 53.8 × 14.1mm - Weight: 101g - Materials: Resin and stainless-steel case/bezel, resin band, mineral glass - Water Resistance: 200m - Shock Resistant - Power: Tough Solar (solar powered) with power-saving mode and battery level indicator - Battery Life: Approx. 5 months (normal use) / 24 months (power save mode) - Bluetooth® Connectivity: Smartphone link with auto time adjustment, phone finder, and access to ~300 world time cities - Functions: Dual time (home city swapping), stopwatch, alarm/hourly signal, full auto-calendar (to 2099) - Light: Super Illuminator LED - Accuracy: ±15 seconds per month (without mobile link) - Other Features: Screw lock crown, energy-saving function, analog display with 3 hands and 3 sub-dials (dual time hour/minute, 24-hour, day)