Micro-adjustment is a clasp feature that lets you change a bracelet’s length in small steps while wearing the watch. It means the fit can be fine-tuned quickly and without tools.
How does a micro-adjusting clasp work?
On a more traditional clasp, a spring bar sits in one of several holes in the clasp sides. Moving it to another hole needs a small tool that pushes the bar in from outside. A micro-adjusting clasp does away with this. On Rolex’s Glidelock, a sliding part locks into a notched rack. The toothed panel sits under the clasp, and the slide-and-lever system moves the bracelet length 2 mm at a time. On Grand Seiko’s clasp, a spring locks the bracelet in place once you let go at the length you want.
How much adjustment does it give?
It depends on the clasp. Glidelock gives up to 20 mm, in 2 mm steps. Grand Seiko’s micro-adjust clasp gives up to about 6 mm, in three steps of 2 mm each. That makes four positions, with the starting position counted as one. On the A. Lange & Söhne Odysseus, a sliding buckle clasp gives about 7 mm. The Tudor Pelagos clasp has three fixed settings. A fourth, automatic setting lets the bracelet stretch and shrink as needed.
Where it comes from
Nobody knows for certain who made the first micro-adjusting clasp. The idea probably began with third-party suppliers, rather than with a watch brand. Rolex brought out its Glidelock clasp in 2008, for dive watches such as the Submariner. Today, some watch clasps offer micro-adjustment that can be used while the watch is being worn. That sets them apart from the more traditional clasp, where changing the fit calls for a tool.
Not to be confused with
Rolex makes two other bracelet systems that work differently from Glidelock. Easylink adds one fixed 5 mm of length by unfolding a link hidden beneath the clasp. There are no steps to choose between. Fliplock is an extension rather than a micro-adjustment. Three blades unfold to make the bracelet about 26 mm longer.
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