On Cloudboom Strike LS Review

The origin story for On’s LightSpray technology seems tailor-made for Hollywood (cue the Damon and Affleck script). It all started on Halloween several years ago, when Johannes Voelchert, the senior lead of innovation technology design for Swiss brand On, watched his kid use a hot glue gun to make a costume. Marveling at how quickly the liquid turned solid, Voelchert wondered if a similar principle could be used in the construction of running shoes.

Five years of tinkering later, On Running has launched its LightSpray technology, which uses a robot that sprays 1.5 km of filament onto a sole to create the upper for the Cloudboom Strike racing shoe.

Initially, the shoe was available only for elite runners to test out prototypes. But after several high-profile finishes — including Helen Obiri’s 2024 Boston Marathon win — proof of concept seemed pretty apparent. Though On released the Cloudboom Strike last year, this is the first model that actually includes the specially made upper that Obiri used in the marathon.

That “LightSpray upper,” which is fused onto a carbon-fiber and foam speedboard by a robot, weighs just 30 g. With On aiming to ramp up production and introduce LightSpray technology into other models, I tested out the Cloudboom Strike LS to find out if the $330 running shoe was worth the hype.

In short: On’s pioneering LightSpray technology can make a lightweight and streamlined running shoe upper in just 3 minutes, while reducing 75% of CO₂ emissions compared to a typical running shoe upper. In my testing, I found the Cloudboom Strike LS a bit difficult to slip on, and it doesn’t offer much versatility outside of road running. But it’s still fast, propulsive, and amazingly lightweight, making the Cloudboom Strike LS my go-to choice for summer runs on pavement.

On Cloudboom Strike LS Review

The Struggle Is Real

During the 2025 Boston Marathon, the On Labs pop-up near the end of the race course was a popular destination, with lines stretching down the block to witness one of two LightSpray robots currently making uppers in the U.S. Visitors could view the tech, try on a Cloudboom Strike LS, and hop on a treadmill to run for a few minutes in the super shoe. 

When I visited, I got to see a lot of people trying to squeeze the shoe on. To construct a one-piece upper that is lightweight and durable, the stretch factor is necessarily limited. Since there are no laces to secure everything, the upper itself has to be robust enough to prevent the foot from sliding around.

So, like a ski boot, there is a certain degree of struggle to get the foot past the smaller ankle opening, especially for those with larger feet. I watched one eager tester shaking and red-faced with effort, attempting to get the shoe on.

The first time I tried on the Cloudboom Strike LS, I was expecting a battle. And yes, there was a minor struggle, but it wasn’t as bad as I thought it would be.

It takes a bit of exertion to get your foot in there, but once it’s in, the upper provides a secure frame without being tight or restrictive. It felt secure, though I wouldn’t want to change direction quickly or take on trails with it, given the upper’s lack of lateral supports. For the activity of road running, though, I’ve never experienced a lighter shoe. And with no pinch points or seams, the upper is chafe-free.

Cloudboom Strike vs. Cloudboom Strike LS

Last year, On released the first iteration of its prototypal “super shoe”: the Cloudboom Strike. That shoe offered the same design used by Obiri in the Boston Marathon — but without the LightSpray upper.

Regardless, that $280 running shoe received a positive review from GJ Contributor Craig Randall. He said the cutting-edge kicks meant that “On will finally rub elbows with super shoe stalwarts like Nike, adidas, and Puma.”

That’s arguably even more true with the release of the same shoe, but upgraded with the LightSpray tech. The main difference between these shoes is all about streamlining the upper. The upper of the Cloudboom Strike, like a traditional sneaker, is composed of multiple materials.

Sneaker uppers often use 20-30 individual pieces of material, and these materials require different production means. The weight — and therefore the environmental impact — quickly adds up.

The Cloudboom Strike weighs 219 g, while the Cloudboom Strike LS clocks in at 183 g. Though this kind of weight difference might not be noticeable on foot, it can have a big impact over longer distances.

A Thrilling Ride

The Cloudboom Strike LS is a propulsive shoe. As I ran along one of my favorite local loops, I wasn’t pushing it. Yet I felt imbued with Pepe Le Pew-like bounciness, effortlessly passing other runners. Sure, it wasn’t a race, but two layers of hyper-foam cushioning with a carbon fiber speedboard in between made for springy strides.

I appreciated that it was cushy without feeling overly squishy, and I was surprised, on checking my metrics after the run, at how much time I’d spent in heart rate zones four and five. The run didn’t feel as strenuous as it was.

On another evening, I went out for a run after a long day of teaching, coaching, and bike commuting and was worried about the general fatigue I’d feel. My muscles were tired, but the lightness of the shoe made my stride feel less effortful than I thought it would.

Despite not logging a ton of miles on that outing, it was nice to run in something with such generous energy return. The upper also offered more breathability than I expected from the one-piece construction.

Pablo Erat, On’s director of footwear emerging technology, said there’s an accessibility to the shoe. It functions well for both weekend warriors and elite athletes, he argued.

“A Ferrari is highly specialized,” Erat told me when we sat down at On Labs before the Boston Marathon. “Yet a Porsche can be enjoyed by a regular driver. This shoe is still amazingly fast, even for runners who are not top-level runners.” 

Like a Porsche, the Cloudboom Strike LS is expensive, with a $330 price tag. But if you are looking to splurge on an elite running shoe, this one is unlike anything you’ve worn before.

The Future of LightSpray

The Cloudboom Strike LS is a test case for how an upper knitted together by a robot in 3 minutes would work. Now that the shoe is on the market, the implications behind future uses of the LightSpray technology are compelling. One robot can make 1,500 shoes a month.

The use of one material in the upper — compared with a typical upper that can be composed of over 11 different materials — also significantly reduces CO₂ emissions. 

On is currently ramping up robot production, and new LightSpray drops are scheduled for July and September. The plan is to have a full portfolio of LightSpray with additional models dropping next year as well.

Availability and Conclusion

The Cloudboom Strike LS has been hard to keep in stock. It’s listed as “For Members” on the On website and says “Coming Soon,” despite having been available only in limited releases. 

If you can get your hands on a pair, you’ll have to shell out $330. But many other “super shoes,” like Nike’s Alphafly ($295) and Puma’s Fast-R Nitro ($300), aren’t exactly bargains by comparison. The high price point is also more palatable when you consider the sustainable mode of production. 

At the end of the day, however, we judge our runners on how they perform at pace. And with the Cloudboom Strike LS the pace is pretty fast, and the ride is particularly pleasant. My pair of Cloudboom Strike LS has held up well through the spring and early summer. I haven’t noticed any stretching to the upper or separation where it connects with the sole.

The Cloudboom Strike LS isn’t the most versatile shoe: it’s not waterproof and doesn’t perform well off the tarmac. But for summer outings on pavement, there’s no doubt it’s the shoe I’ll be reaching for.