Grand Seiko Unveils New Spring Drive U.F.A. Ushio Divers

Grand Seiko Redefines Precision Diving with the Spring Drive U.F.A. Ushio 300

At Watches and Wonders Geneva 2026, Grand Seiko unveiled a significant evolution in its diving lineup: the Spring Drive U.F.A. Ushio 300 Diver. By combining a more compact case with the brand’s most accurate mainspring-powered movement, Grand Seiko has addressed a long-standing request from enthusiasts for a smaller, high-performance diver’s watch.

The Evolution 9 Collection: Design and Dimensions

The Ushio 300 Diver joins the Evolution 9 Collection, focusing on ergonomic design and technical precision. The watch features a case diameter of 40.8mm and a height of 12.9mm, making it Grand Seiko’s smallest diver’s watch to date.

Constructed from High-Intensity Titanium, the case balances strength with lightness. To ensure versatility and comfort whether the wearer is on land or underwater, Grand Seiko implemented an Evolution 9 ergonomic design and a newly developed extension clasp with micro-adjustment.

Technical Mastery: The Caliber 9RB1

The heart of the Ushio 300 is the new Spring Drive Caliber 9RB1. This movement represents a leap in precision for mainspring-powered watches, achieving an accuracy of ±20 seconds per year. This level of performance earns the watch its U.F.A. (Ultra Fine Accuracy) designation.

Key technical features of the 9RB1 movement include:

• Vacuum-sealed oscillator: Minimizes external interference to maintain precision.
• Thermo-compensated IC: Adjusts for temperature fluctuations that could affect timing.
• Offset magic lever: Enhances winding efficiency.
• Power Reserve: Provides three days of autonomy.

Aesthetic Details and Legibility

The Ushio 300 is available in two primary models: the SLGB023 (Ushio Blue) and the SLGB025 (Ushio Green). The SLGB023 features a gradient blue dial designed to capture the depth of the open ocean, complemented by the Ushio wave pattern that reflects light across the surface.

For maximum utility underwater, the watch includes:

• A 120-click unidirectional ceramic bezel.
• Diamond-cut rectangular indexes.
• Broad hour and minute hands for enhanced legibility.

Frequently Asked Questions

What makes the U.F.A. Designation special?

The U.F.A. (Ultra Fine Accuracy) designation is reserved for movements that reach extreme precision. The Caliber 9RB1 achieves this via a vacuum-sealed oscillator and thermo-compensation, resulting in a deviation of only ±20 seconds per year.

When will the Ushio 300 Diver be available?

According to official boutique listings, the SLGB023 is expected to ship in June 2026.

How does the case material benefit the wearer?

The use of High-Intensity Titanium ensures the watch remains lightweight and resistant to corrosion, which is essential for a professional diving instrument.

With the launch of the Ushio 300, Grand Seiko successfully merges the rugged requirements of a professional diver with the obsessive precision of the Spring Drive movement, setting a new benchmark for the Evolution 9 Collection.