Grand Seiko expands its Evolution 9 Collection with the introduction of the Spring Drive U.F.A. Ushio 300 Diver SLGB023 and SLGB025.
These two new references are powered by the Calibre 9RB1, a movement that offers an annual accuracy of ±20 seconds—positioning it among the most precise wristwatch movements ever powered by a mainspring.
The designation U.F.A., standing for “Ultra Fine Accuracy,” was established in 2025 with the release of Calibre 9RB2. The new 9RB1 builds on this development, maintaining the same performance standards while adapting the architecture to a dedicated diver’s format.
The movement operates with a self-winding system, delivers a power reserve of approximately 72 hours, and runs at the typical Spring Drive glide motion regulated electronically via a quartz oscillator.
To achieve this level of accuracy, the oscillator and integrated circuit are vacuum-sealed and individually calibrated, with thermo-compensation data programmed into the circuit.
Housed in a 40.8 mm case with a thickness of 12.9 mm, these models represent the most compact Grand Seiko diver’s watches to date.
Both case and bracelet are crafted from High-Intensity Titanium, a material approximately 30% lighter than stainless steel, contributing to improved comfort while maintaining high resistance to corrosion and wear.
Water resistance is rated to 300 metres / 1,000 feet, supported by a screw-down crown and caseback.
The unidirectional bezel features 120 clicks for precise adjustment and is fitted with a ceramic insert for enhanced scratch resistance.
Legibility, a key aspect of the Evolution 9 design language, is ensured by large, multi-faceted applied indexes and sharply defined hands, all treated with Lumibrite.
The two models are distinguished by their “Ushio” dials, a theme inspired by the sea and introduced in previous Grand Seiko diver’s watches. The term “ushio”, meaning “tide” in Japanese, is reflected in textured dials with gradient colouring.
The SLGB023 features a deep blue tone evoking the open sea, while the SLGB025 adopts a green shade inspired by coastal waters. The power reserve indicator is positioned on the dial side.
The titanium bracelet is equipped with a newly developed locking extension clasp.
This system offers a three-step micro-adjustment of 6 mm, alongside an additional 18 mm extension for use over a diving suit, providing a total adjustment range of 24 mm.
The Grand Seiko Spring Drive U.F.A. Ushio 300 Diver will be available from June 2026 at Grand Seiko boutiques and selected retailers, with a recommended retail price of €12,500 for each reference. grand-seiko.com
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