On reveals ‘LightSpray’ technology on Cloudboom Strike LS

The brand’s revolutionary spray-on upper removes the need for laces. But is this super shoe worth the £330 price tag?

Following months of secrecy, Swiss sportswear brand On unveiled its revolutionary new LightSpray technology earlier this summer: an ultralight, one-piece upper that’s sprayed onto the shoe by a robotic arm.

Yep, 2023 might have been the year of the midsole, but in 2024, the upper is having a moment. LightSpray is made in a fast, one-step manufacturing process, automated by a robotic arm at the On Labs in Zurich. It’s ultra-thin, adaptable to the foot, seamless and lace-free. And according to On, each shoe is fully assembled in just three minutes.

But those aren’t the only benefits. On claims the technology reduces an upper’s carbon emissions by 75% compared with its other racing shoes.

‘LightSpray marks a significant milestone for On, not only in creating high-performance products but also the potential it has to move us towards a more sustainable, circular future,’ says Marc Maurer, co-CEO of On. This is thanks to the upper’s construction from a single recyclable material and the assembly process that eliminates the need for glue.

The Cloudboom Strike LS (LightSpray) is the brand’s first high-performance running shoe to feature the technology. Weighing in at just 188g (UK size 8.5) – including a 30g upper – Hellen Obiri wore a development version to win the 2024 Boston Marathon in April and placed second in the shoe at the 2024 New York City Marathon.

The non-LightSpray version (with a technical mesh upper) is already widely available, but the LS isn't set to launch until later this year. I was one of five lucky people in the UK to get their hands on a pair ahead of their launch and understandably, I’ve been asked a lot of questions about them: How do they really fit? Do they really feel stable? Are they breathable?

Having tested the shoe over the past couple of months, here’s my verdict.

I'm usually keen to get onto the midsole as quickly as possible when it comes to reviewing a new running shoe, but let's face it, the upper is the star of the show here and fit is the question on everyone’s lips with the Cloudboom Strike LightSpray. With no heel counter, no lacing system and no overlays, you’re relying purely on the upper moulding around your foot in order to get a secure lockdown.

I won’t beat around the bush – this isn’t the easiest shoe to get on, especially with no heel tab. But then again, a shoe with no laces needs to be tight in order to secure your foot in place, which is why the opening is very narrow. I’ve found if I insert my foot slightly sideways into the shoe until about halfway, I can get two fingers down the back to pull the heel out slightly (the material has a tiny bit of give) and then wriggle/dance my foot forward until it slips in. If this sounds like a faff, remember, you've got no laces to tie: I timed it and it took me approximately 11.19 seconds. For comparison, the Alphafly 3 took me 16.14 seconds to get on.

Now, I had all the same questions everyone has when it came to the upper. Namely, 'how on earth is this going to hold my foot in place?'. Well folks, trust me when I say: it just does. The technology comfortably moulds around my foot, with no stretching, slipping or instability. It's weird, but it's pretty cool.

However, it's worth noting that I have a pretty average foot – I wear a UK 8.5 in almost all of my running shoes, including On, and the Cloudboom LightSpray is no exception. If you do have a wider or narrower foot, I can’t say whether the technology will mould around your foot as well. Perhaps in the future, On will look to personalise the shoe to more foot types. For now, we've just got this standard option and I'm lucky that it works fine for me.

The LightSpray material itself is surprisingly strong – after three months running in these, I’ve not seen any sign of tearing or stretching. They still hold my feet in place just as well as the first time I put them on. Breathability hasn't been an issue for me either.

Oh, and in case anyone's wondering, when it came to the question of ‘socks or no socks?’, I took Obiri’s lead with these and opted for my usual quarter-length number.

The shoe’s midsole (39.5mm/35.5mm, 4mm drop) features two layers of Helion HF Hyper foam, a Pebax formula made with over 40% bio-based raw materials, and a Speedboard – On’s version of a carbon plate – sandwiched between the foam to aid propulsion.

The ride has that bouncy and propulsive feeling you’d expect from a carbon-plate shoe and you can really feel the responsiveness – way more than the Cloudboom Echo 3 which felt a lot stiffer and harder work. At the same time, it's not aggressive like the Saucony Endorphin Elite or even the Hoka Cielo X1. In fact, it probably leans more towards the Asics Metaspeed Paris models (188g) on the Vaporfly 3 (198g) in terms of that light, on-the-foot feeling and like the Metaspeed Paris models, the lower heel-to-toe drop is probably going to be a smarter bet for forefoot strikers and midfoot runners.

Like a lot of On's running shoes, I would say that the Cloudboom Strike LS feels slightly firmer underfoot. That’s not a criticism, though; it’s not uncomfortable or harsh, it just offers a solid platform for push-off and there's still a decent amount of cushioning overall to see you through a half-marathon or marathon.

The main catch of the shoe, though, is the price. At £330, this is one of the most expensive racing shoes on the market, second to only the Adidas Adios Pro Evo 1. I never thought I'd be using the words 'Alphafly' and 'cheap' in the same sentence, but even Nike is going to be a more 'affordable' option here.

Make assumption all you want, but the On Cloudboom Strike LS is undeniably a trailblazer, and having run in the shoe over the past few months, I believe the brand has delivered an impressive innovation with its LightSpray technology. Yes, getting the shoe on might take some getting used to, and I'm definitely fortunate to have more of a 'standard' foot shape to accommodate the technology, but the ultralight one-piece upper moulds closely around the foot for a secure lockdown that defies doubts about stability or slippage.

Performance-wise, the midsole delivers a bouncy and propulsive feel without veering into an overly aggressive or rigid territory. And while these definitely aren't made for easy runs or gentle plodding, you don't need to work as hard in them as the Cloudboom Echo 3.

But are they worth the £330 price tag? The jury's out on this one. Sure, it's a great shoe; it's fun, it's bouncy and it's lightweight — but so are the Metaspeed Sky Paris (£220) and the Vaporfly 3 (£239.99) and both of those have been hitting the podiums of the Majors this year, too.

The Cloudboom Strike LS is undoubtably On's best racing shoe yet, but it's a concept shoe, designed for tech-minded racers with a budget to match. If you can forgo a few extra grams, I'd probably tell you to spare your money — and your curiosity — and opt for a more 'affordable' speed shoe instead.

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