Grand Seiko Evolution 9 Automatic Men's 40.80mm Watch SLGB023

The Grand Seiko Evolution 9 SLGB023 "Ushio 300" is a Spring Drive diver's watch and the most compact diver in the current Grand Seiko range, with a case diameter of 40.8mm designed to suit a broad range of wrist sizes without sacrificing the presence expected of a genuine dive tool.

This timepiece is powered by the Calibre 9RB1, a Spring Drive movement hand-assembled by watchmakers at the Shinshu Watch Studio, part of a Seiko Epson facility in Shiojiri, Nagano Prefecture. It shares its core architecture with the Calibre 9RB2 — the movement that introduced Grand Seiko's "Ultra Fine Accuracy" (U.F.A.) designation and, as of April 2026, holds the distinction of the most accurate mainspring-powered wristwatch movement on record, rated to ±20 seconds per year. On the 9RB1, the power reserve indicator sits on the dial side rather than the caseback, giving owners a visible read on the watch's approximately 72-hour (3-day) reserve at a glance.

The dial carries the "Ushio" theme, meaning "tide" in Japanese, a design language that has run through Grand Seiko's diver's watches since 2022. Here it appears in a deep blue gradient intended to suggest sunlight filtering down through open ocean water, paired with the faceted indexes and boldly proportioned hour and minute hands characteristic of the Evolution 9 Style for strong legibility underwater and at a glance.

Case and bracelet are both crafted from High-Intensity Titanium, roughly 30% lighter than stainless steel while retaining a bright, polished lustre rather than the matte finish typical of titanium sports watches. The case is finished with a unidirectional rotating bezel, a screw-down crown, and a screw case back, and carries a 300m water resistance rating, placing it firmly in genuine dive-tool territory rather than desk-diver aesthetics alone.

The bracelet's locking extension clasp offers a three-step micro-adjustment of up to 6mm for everyday fine-tuning, plus a dedicated 18mm diving-suit extension — a combined 24mm of total adjustment, allowing the watch to be worn comfortably over a wetsuit sleeve as well as bare wrist. LumiBrite is applied to the hands, indexes, and bezel pip for legibility in low-light and underwater conditions, and the sapphire crystal carries an anti-reflective coating on its inner surface to minimise glare.