Grand Seiko’s New Spring Drive Just Redefined Accuracy As We Know It (And Finally Fixed Their Bracelet)

Accuracy in watchmaking has always been something of a losing battle for mechanical watchmakers. The humble quartz watch settled that debate decades ago, leaving luxury mechanical watches to compete in areas like craftsmanship, heritage, and emotional appeal rather than pure precision. Grand Seiko, however, has never been content with this arrangement. With their latest release at Watches & Wonders 2025, the Japanese brand has fundamentally redefined what accuracy means for a mechanically-powered timepiece—while simultaneously addressing one of their most persistent customer complaints.

The Numbers Don’t Lie: ±20 Seconds Per Year

Let’s start with the headline: Grand Seiko’s new Spring Drive Caliber 9RB2 boasts an accuracy rating of ±20 seconds per year. Not per day. Not per month. Per YEAR.

To put that in perspective, a standard COSC-certified chronometer is rated at -4/+6 seconds per day, which translates to roughly ±150-180 seconds per month or roughly ±1,800-2,200 seconds per year. Even Grand Seiko’s previous Spring Drive movements, with their impressive ±15 seconds per month accuracy, would drift up to ±180 seconds in a year’s time. This new U.F.A. (Ultra Fine Accuracy) movement improves on that by a factor of nine.

This achievement is a case of Grand Seiko doing what they do best—quietly pushing the technical boundaries of watchmaking while everyone else is distracted by marketing hype. The U.F.A. designation harkens back to the brand’s V.F.A. (Very Fine Adjusted) watches from 1969 to 1975, which were legendary for their precision. It’s a fitting tribute that underscores Grand Seiko’s unwavering pursuit of performance excellence over more than six decades.

How They Did It

Spring Drive has always represented a brilliant middle path between mechanical and quartz watchmaking. Instead of using an escapement to regulate timekeeping (like a mechanical watch) or a battery-powered oscillator (like a quartz watch), Spring Drive uses a mechanically-wound mainspring to power a quartz oscillator through an electromagnetic generator.

For the new U.F.A. movement, Grand Seiko has refined this system further with enhanced manufacturing processes for the three-month-aged quartz oscillator and a newly designed integrated circuit. Each oscillator is measured at various temperatures, with the resulting data programmed into a low-power IC for thermal compensation. Both the oscillator and sensor are vacuum-sealed to minimize temperature differences and protect against external factors like humidity and static electricity.

The 9RB2 also introduces a regulation switch that can be used during servicing to correct any accuracy drift over time—essentially future-proofing your investment. And all this comes in a compact 30mm × 5.02mm package that still delivers Spring Drive’s signature 72-hour power reserve.

Two Case Studies in Excellence

Grand Seiko is introducing the U.F.A. movement in two distinctly different models, both housed in the brand’s Evolution 9 case design.

The SLGB001 is the luxe option—a limited edition of 80 pieces in 950 platinum, paired with a blue crocodile strap and available exclusively through Grand Seiko boutiques for $39,000. It’s undeniably stunning, with a light blue textured dial inspired by the frost-covered trees of Japan’s Kirigamine Highlands.

But it’s the non-limited SLGB003 that deserves the spotlight. This $10,900 model comes in Grand Seiko’s High-Intensity Titanium, which combines the lightweight properties of titanium with excellent scratch resistance. Its silver-tinged blue dial has the same ice forest texture but with slightly cooler tones, and it’s complemented by a tempered blue seconds hand that adds a subtle splash of color.

The Revolution Is In the Clasp

While the accuracy story is headline-grabbing, there’s another significant upgrade that longtime Grand Seiko fans will be ecstatic about: the SLGB003 debuts a brand new bracelet clasp with a three-step toolless micro-adjustment system. This allows on-the-fly adjustments in 2mm increments, providing up to 6mm of total adjustment range without needing tools.

This might sound trivial to the uninitiated, but the lack of an easy adjustment system has been one of the few consistent criticisms of Grand Seiko’s otherwise excellent bracelets (and something that we’ve been vocal about with every brand at this point). In a world where wrists swell and contract throughout the day, the ability to quickly adjust your bracelet without hunting for a toothpick or spring bar tool is a genuine quality-of-life improvement that elevated brands like Rolex and Tudor have offered for years.

Smaller Is Better

Both models measure just 37mm in diameter with a thickness of 11.4mm, making them the smallest Evolution 9 watches to date and the smallest Grand Seiko models ever to use a 9R-series movement. This more modest sizing represents a welcome trend toward wearability that we’re seeing across the luxury watch industry.

Despite the restrained dimensions, the watches maintain Grand Seiko’s signature Zaratsu polishing and a respectable 100-meter water resistance. The dial texture is subtle enough to avoid being gimmicky but distinctive enough to catch the light in intriguing ways, a perfect embodiment of the brand’s knack for dialing in just the right amount of visual interest.

Spec Sheet

Pricing & Availability

The Grand Seiko Spring Drive U.F.A. SLGB003 in High-Intensity Titanium will be available at Grand Seiko Boutiques and selected Grand Seiko Salons starting in June 2025, priced at $10,900. The platinum SLGB001 is limited to 80 pieces, available exclusively at Grand Seiko Boutiques for $39,000.

Recap

Grand Seiko Spring Drive U.F.A. SLGB001 and SLGB003

Grand Seiko redefines accuracy with the new Spring Drive U.F.A. movement, accurate to an astonishing ±20 seconds per year, housed in a perfectly sized 37mm Evolution 9 case with frost-inspired dial texture and—finally—a toolless micro-adjustable bracelet on the titanium SLGB003 model.

Learn More: Grand Seiko