In 2025, 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.* This model is powered by Caliber 9RB1, featuring an improved construction that makes it ideal for sporting conditions while sharing the same attributes as the Caliber 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.
Exterior
Exterior: High-Intensity Titanium
Case back: Screw case back
Glass Material: Sapphire crystal
Glass Coating: Anti-reflective coating on inner surface
LumiBrite: LumiBrite on hands, index(es) and bezel
Case size: Diameter 40.8mm Lug-to-lug 48.5mm Thickness 12.9mm
Band width: 21mm
Clasp type: Locking extension clasp with micro-adjustment
The perimeter of Band:195mm
Movement
Caliber no.: 9RB1 Instructions
Movement Type: Spring Drive
Power reserve: Approx. 72 hours(3 days)
Accuracy: ±20 seconds per year (±3 seconds per month)
Functions
Water resistance: 300m / 1000ft diver's
Magnetic resistance: 4,800 A/m
Weight: 122 g
Other details / Features:
Unidirectional rotating bezel
Screw-down crown
Allergy-safe metal
33 jewels
Power reserve indicator
