The engineering of lightness: Part 2 — the material science behind 0.05 mm
In the previous article, we explored the front end of OpenFit Air 2: the spherical drivers, custom battery, and 30°/14° acoustic geometry that help deliver both compact size and powerful sound within a 7.2g design.
But roughly half of the earbud’s weight, and much of what determines whether it stays securely in place, comes down to the ear hook.
Here’s the engineering paradox: when reducing weight, most components need less material—but one critical part needs more.
Not every weight-saving strategy actually saves weight
The ear hook is one of the most important areas for reducing weight. Because silicone is relatively dense and makes up a substantial portion of the hook, the obvious solution is to make it narrower, thinner, and shorter.
Engineers explored another idea in the previous-generation OpenFit Air: a hollow ear hook. On paper, using less material should have reduced the weight; in practice, however, the silicone walls had to become thicker to maintain structural integrity, resulting in a heavier design.
That approach was ultimately abandoned.
Instead, OpenFit Air 2 takes a simpler, more effective path:
● Eliminate the hollow structure.
● Reduce the outer thickness from 7 mm to 5 mm.
● Shorten the overall hook by 2 mm.
● Further slim and narrow the tip.
Together, these changes reduce weight while also allowing for a smaller, more portable charging case.
Hollow hooks looked lighter on paper—but thicker silicone made them heavier in practice.
The counterintuitive 0.05 mm upgrade
While the silicone surrounding the ear hook became lighter, the internal support frame moved in the opposite direction.
Many open-ear hooks use 0.7 mm or thinner Ni-Ti alloy wire to minimize weight. OpenFit Air 2 instead increases the wire diameter to 0.75 mm【1】. Although that adds only 0.05 mm, it increases the amount of material by roughly 10%.
That decision wasn't made to add strength for its own sake—it was driven by the mechanical requirements of an open-ear design.
Because open-ear earbuds don’t sit inside the ear canal, long-term stability depends heavily on the ear hook. When the support wire is too thin, high-intensity movement can cause:
● The earbud to bounce during activity.
● The speaker to shift away from its optimal position.
● Reduced bass performance and a less secure feel.
The thicker wire better resists bending, helping maintain a consistent distance between the driver and the ear throughout movement. The result is a more stable fit and more consistent acoustic performance during running, strength training, and other high-intensity exercise.
The thicker wire also improves long-term durability. Repeated bending naturally fatigues metal over time, and thinner frames can gradually loosen. The 0.75 mm design helps preserve a consistent fit not just on the first day of use, but after years of everyday wear.
0.75 mm titanium wire trades 0.05 mm of weight for clamping force that keeps the driver locked in place.
Stability comes from balance, not clamping force
Many open-ear earbuds improve stability by simply increasing clamping force. While that can make the earbud feel more secure, it can also create discomfort during extended wear.
OpenFit Air 2 takes a different approach by balancing three interacting forces:
● The support provided by the outer ear.
● The friction created by the soft silicone surface.
● The opposing holding forces between the front pod and the ear hook.
Together, these forces create a three-dimensional support system. The upper portion rests lightly on the ear, the silicone naturally conforms to the skin, and the 0.75 mm Ni-Ti alloy wire anchors the earbud behind the ear.
Within that system, the thicker wire plays a critical role. Much like the main cable of a suspension bridge, it provides the rigidity needed to counter the inertia created by walking, running, and high-intensity workouts, helping keep the driver in its optimal position.
Shokz summarizes this philosophy in four word: Firm frame. Flexible fit.
The goal of a 7.2g earbud was never simply to make it lighter. It was to make it lighter without sacrificing stability. That extra 0.05 mm of wire became the structural foundation that makes both possible.
Next: Part 3: The experience of lightness, proven by data. Discover how Shokz engineers validated barely-there comfort through months of testing across real ear shapes, movement scenarios, and everyday listening.
【1】0.75 mm titanium wire data gathered from Shokz Lab.
