SLGB023 SLGB023G

The “Ushio 300,” a Spring Drive diver’s watch with phenomenal accuracy and a stunning blue dial

In 2025, Grand Seiko unveiled the Spring Drive Calibre 9RB2, a groundbreaking movement that received the then-new U.F.A. designation, standing for “Ultra Fine Accuracy.” Boasting an annual accuracy rate of ±20 seconds, Calibre 9RB2 earned the distinction of being the most accurate wristwatch movement powered by a mainspring.* This model is powered by Calibre 9RB1, featuring an improved construction that makes it ideal for sporting conditions while sharing the same attributes as the Calibre 9RB2.

The term "ushio", which means “tide” in Japanese, evokes the waters that surround the Japanese archipelago. This creation’s blue dial reflects the vast expanse of the sea through a gradient that captures light streaming into the deep ocean.

* As of April 2026, based on Grand Seiko’s research."

Any purchase through our Grand SEIKO Online Store has a 5 Year limited guarantee