2026

Mar.17, 2026

MinebeaMitsumi's World's Smallest Bearing Selected for ŌTSUKA LŌTEC's Watch "No.8"
- Supporting the drive of a complex mechanism, where diverse motions perform in harmony within a glass enclosure -

MinebeaMitsumi Inc. (head Office: Nagano Prefecture, Representative Director, Chairman CEO: Yoshihisa Kainuma; hereinafter referred to as "MinebeaMitsumi") is pleased to announce that MinebeaMitsumi's ball bearings, including the world's smallest ball bearing^*, have been selected for "No.8," the mechanical watch from the the Japanese watch brand, ŌTSUKA LŌTEC, following their previous use in the "No.5 KAI" and "No.9" models.

"No.8"

(Left) MinebeaMitsumi's World's smallest bearing/(Right) Miniature Ball Bearing

ŌTSUKA LŌTEC, a Japanese watch brand, was established by Jiro Katayama, a recipient of the Contemporary Master Craftsman Award^** and winner of the Grand Prix in the "Challenge Watch Prize" Category (for watches priced at 3,000 Swiss Francs or less) at the 2024 Le Grand Prix d'Horlogerie de Genève (GPHG), known as the Academy Awards of the watch world.
This mechanical watch "No.8" by ŌTSUKA LŌTEC has a unique display mechanism that showcases various motions within the glass enclosure every hour. On the hour, the hour display instantly switches through the rotation of the hour channel, while the fader for displaying minute, which interlocks with the flywheel, goes back from the 60-minute mark to zero. The side of the watch is made of glass, offering a view of the minute-displaying fader lever passing through between two-story faces. Moreover, the second disk, which rotates once every 90 seconds, is placed on the upper part of the faces.
To drive these complex motion, "No.8" employs ŌTSUKA LŌTEC-made module above the MIYOTA-made movement. The number of parts used in this module totals 62. Within this elaborate module, three MinebeaMitsumi's ball bearings are integrated; one unit of the world's smallest ball bearing with an outer diameter of 1.5 mm, and two units with an outer diameter of 2.5 mm. These three bearings play a role in supporting the seamless drive of the complex mechanism.

* Minebea's Bearing with 1.5 mm in Outer Diameter achieved a GUINNESS WORLD RECORDS™ title for the Smallest Commercially Available Steel ball bearing (Our press release issued on August 31, 2015)

• ** Contemporary Master Craftsman Award: "Award for Outstandingly Skilled Workers" given by the Ministry of Health, Labor and Welfare since 1967.

About MinebeaMitsumi's Miniature Ball Bearing

MinebeaMitsumi's ball bearing, the company's original business and starting point, is driven by the ultra-precision technology cultivated over 70-year pursuit of excellence. The company internally encompasses a wide range of production aspects, from machining cutting tools, jig and tools, production facilities, environmental measures, and development of advanced machining technologies, to maintain the machining precision by controlling nanometer-scale machining dimensions.
The manufacturing process from cutting to the final process of the specially made ruby ball bearing and the world's smallest ball bearing are manually manufactured by a limited number of the company's engineers.
This ultra-precision machining technologies and vertically integrated production system are one of MinebeaMitsumi's core competences.

MinebeaMitsumi's Karuizawa Plant

The Scene of Hand-Assembling Ball Bearing (Photo taken at Karuizawa Plant, Head Office)

Overview of ŌTSUKA LŌTEC's "No.8"

Function	Hour channel (Jumping hour)/Minute fader (Flywheel-Linked Retrograde Mechanism)/Second disk
Drive System	Automatic winding
Movement	MIYOTA 90S5 + ŌTSUKA LŌTEC-made module (Automatic winding, 33 stones + 3 ball bearings, 28,800 vph, approx. 32 hours of power reserve)
Case Size	31 mm in width (lug to lug: 47.8 mm)
Case Thickness	10.8 mm
Material	Stainless steel (316L)
Case Finish	Hairline finish
Case Back	Solid back
Water Resistance	Daily life waterproof (3 ATM)
Watch Glass	Sapphire crystal glass (Anti-reflection coating and anti-fingerprint coating)
Strap	Rubber (Lug width: 24 mm)
Price Inc. Tax	990,000 yen (with one-year warranty)
Movie	https://youtu.be/i-KcUA1wrZQ

Actual Unit Exhibition

Period	Thursday, March 19, 2026 – Monday, March 23, 2026
Time	10:00am - 7:50pm (Closes at 7pm on 23rd)
Venue	WITH HARAJUKU, 1F entrance (1-14-30, Jingumae, Shibuya-City, Tokyo)
Entrance Fee	Free
URL	https://withharajuku.jp/

About ŌTSUKA LŌTEC

ŌTSUKA LŌTEC is the Japanese watch brand founded in 2012 by Jiro Katayama, a recipient of the Contemporary Master Craftsman Award. All of its watches are meticulously crafted in-house under the direction of Mr. Katayama. His career began as a car and product designer, but after winning a bench lathe through an online auction in 2008, he shifted to watchmaking and selling his watches in 2012. His creation "No.6" was awarded the Le Grand Prix d'Horlogerie de Genève 2024 in the "Challenge Watch Prize" category (for watches priced at 3,000 Swiss Francs or less).

Website

About MinebeaMitsumi

MinebeaMitsumi is an INTEGRATED^*** precision components manufacturer. The company specializes in ultra-precision technologies, ranging from core products such as miniature and small-diameter ball bearings—which ensure smooth machine rotation—to protection ICs for single-cell lithium-ion batteries. The company's diverse portfolio includes motors, sensors, and semiconductors. While often unseen, MinebeaMitsumi's ultra-precision technologies support daily life across a wide array of fields, including home appliances (air conditioners, vacuum cleaners, and hair dryers), gaming consoles, IT devices like smartphones and PCs, as well as automotive, aerospace, and medical equipment.

Website

• *** This term was adopted with the intended meaning "to be combined" rather than "to sum up." Create new value through synergy by combining all the resource across the company's group.

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