Grand Seiko Evolution 9 Collection Spring Drive U.F.A. Ushio 300 Diver: SLGB023, SLGB025

Introducing the Spring Drive U.F.A. Ushio 300 Diver, Grand Seiko’s smallest diver’s watch and the most accurate with a Spring Drive movement.

At last year’s Watches and Wonders Geneva, Grand Seiko unveiled the Spring Drive Caliber 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, Caliber 9RB2 earned the distinction of being the most accurate wristwatch movement powered by a mainspring.* Today, Grand Seiko introduces into the Evolution 9 Collection two new diver’s watches powered by a new Spring Drive U.F.A. movement, Caliber 9RB1.

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

A diver’s watch true to the ideals of Grand Seiko

Like every Grand Seiko watch, the new creation strikes a perfect balance between function and beauty. The new creation’s legibility, durability, and wearing comfort have been thoroughly considered and painstakingly engineered to ensure uncompromising performance in any environment. Commensurate attention has been given to every aspect of the watch’s physical appearance.

The 120-click bezel allows for precise adjustment, while the ceramic bezel insert provides excellent resistance to scratches and corrosion.

The prominent indexes of the Evolution 9 Style are meticulously crafted with multiple facets. The edges and sides of the indexes are precisely diamond-cut for exceptional brilliance, while their rectangular shape accommodates sufficient Lumibrite for superb legibility in any lighting condition. Both the hour and minute hands strike a sharply defined and powerful form, ensuring outstanding legibility at a glance.

The new creations showcase blue and green variations of the “Ushio” dial, a design theme that has been part of the Grand Seiko diver’s watch since 2022. The term ushio, which means “tide” in Japanese, evokes the waters that surround the Japanese archipelago, a timeless source of inspiration in Japan’s culture and art. Combined with a gradient design, the vivid dial colors of the new creations emphasize the “Ushio” pattern while ensuring the excellent legibility for which Grand Seiko diver’s watches are renowned. The blue dial reflects the vast expanse of the sea through a gradient that captures light streaming into the deep ocean, while the green dial draws from the tranquil beauty of shallow coastal waters near the shore.

Enduring strength meets comfort and versatility

The lugs are designed with a broad profile to capture light across a wide surface, enhancing the watch’s presence on the wrist despite its compact size.

Thanks to the movement’s compact design, the new models feature a case diameter of just 40.8mm, the smallest of any Grand Seiko diver’s watch, ensuring a comfortable fit for a wide range of wrist sizes. Both the case and bracelet are crafted from High-Intensity Titanium, a material approximately 30% lighter than stainless steel and distinguished by its bright, lustrous tone.

The bracelet includes a newly developed locking extension clasp with micro-adjustment. In addition to a three-step micro-adjustment that allows for up to 6mm of fine-tuning, the extension feature, designed to be used with a diving suit, enables an additional 18mm, providing a total of 24mm of adjustment.

The GS emblem on the clasp functions as a locking mechanism, preventing the accidental release of the clasp.

As the name of the new watches suggests, they are water resistant to 300 meters, showcasing their high durability. Combined with the scratch resistance and light weight of High-Intensity Titanium, each timepiece offers exceptional robustness and wearing comfort.

The latest Spring Drive U.F.A. movement: Caliber 9RB1

The power-reserve indicator has been repositioned to the dial side.

The 9RB1 movement is hand-assembled by the highly skilled craftsmen and women of the Shinshu Watch Studio, located in a Seiko Epson facility in the city of Shiojiri in Nagano Prefecture. The movement’s annual accuracy of ±20 seconds is achieved by vacuum sealing the crystal oscillator, which has been stabilized through a three-month aging process, together with the IC, minimizing the influence of external factors such as temperature, humidity, static electricity, and light. Each oscillator’s frequency is measured at multiple temperatures, and the resulting data is programmed into the low-power IC to enable precise thermo-compensation. The movement features a regulation switch that can be used during after-sales service to correct any divergences in accuracy that may occur over long periods of use.