On Cloudboom Strike LS Review: Boston's LightSpray Super Shoe

The On Cloudboom Strike LS is the premium version of On's racer, with a robot-sprayed LightSpray upper: no laces, no seams. Supercritical Helion HF foam, Speedboard carbon plate, 73.4% energy return in the forefoot. Hellen Obiri wore it to win the Boston Marathon. Price: €330 for the premium edition. As a RunMorph coach, I see a technology showcase that pushes the very idea of a racing shoe into new territory.

On invents the super shoe without a stitched upper

The Cloudboom Strike LS is the LightSpray version of the classic Cloudboom Strike. The big difference: the upper is neither woven nor stitched. A robot sprays it directly onto the foot. The result is a 30 g technical sock with no seams, no laces and no pressure points. This is genuine industrial innovation, not a marketing stunt.

The LS sits at the top of On's racing lineup, above the On Cloudultra 3 (trail-oriented) and the classic Cloudboom Strike (with traditional laces). In France, you can buy it from on.com/fr-fr and i-Run. It sells for 329.95 USD in the US and around €330 in France.

© On Running, official photo used for editorial purposes

RunMorph's advice

If you want the cutting edge of road racing tech and price is no obstacle, the Cloudboom Strike LS is a one-of-a-kind experience. For 90% of runners who want a true carbon super shoe at a reasonable price, go for the Nike Vaporfly 4, the Asics Metaspeed Sky Tokyo or the Saucony Endorphin Pro 5 instead. The LS is for the runner who wants the very best and the thinnest, most slipper-like feel on the market.

Objective technical specs

Three standout numbers: 215 g for 39.5 mm of stack (very light), 73.4% energy return in the forefoot (world-class, on par with the Nike Vaporfly 4) and 30 g for the LightSpray upper alone (lighter than a sock).

The 4 mm drop is typical of modern racing super shoes. The Speedboard plate is a carbon-reinforced nylon-TPU with a spoon-shaped design that channels energy return forward. The Bounceboard is an extra drop-in foam layer that amplifies the bounce. This multi-layer build is more complex than a Metaspeed Sky Tokyo, but you feel the payoff in the shoe's dynamics.

Who is this shoe for?

Elite runners and ambitious racers (sub-2:45 marathon, sub-1:20 half)

This is its core audience. The Cloudboom Strike LS is built for fast times. If you are chasing a sub-2:45 marathon or a sub-1:20 half, you will appreciate every microsecond gained from the superior energy return, the ultralight upper that weighs next to nothing and the carbon plate that never quits. On Pro Team athletes (Hellen Obiri, Yared Nuguse, Ben Connor) race in it at world level.

Premium runners who want the most advanced experience

At €330, this shoe targets runners who want to try the best there is, regardless of value for money. If you have already tried the Vaporfly 4, the Adios Pro Evo 3 and the Metaspeed Sky Tokyo, and you want to explore On's racing philosophy, the LS is the shoe to try.

Runners who value a slipper-like feel

The LightSpray upper is unique on the market: it molds to your foot like a second skin, with no pressure points and no seams to rub. If you are prone to blisters, or struggle to find a shoe that stays comfortable beyond 2 hours of running, the LS can be a revelation. The sprayed fabric breathes better than a classic woven mesh.

© On Running, official photo used for editorial purposes

On the run: what you will feel

Putting it on is unlike anything else. With no laces, the shoe slides on like a compression sock. The upper moves freely and your foot slips in without friction. First contact with the ground: the Helion HF foam bounces back instantly, the Speedboard plate flexes under your foot and the Bounceboard amplifies the sensation. The rebound is more controlled than a Vaporfly 4 and more dynamic than an Endorphin Pro 5.

At marathon pace (3:30/km to 4:30/km), the shoe hits its sweet spot. The pronounced rocker, the plate pulling you forward, the upper that stays put without constricting: you glide. At 30 km, you realize you have not thought about your shoes once, and that is exactly what you expect from an elite super shoe.

At half marathon pace (3:00/km to 3:30/km), the shoe responds even better. You feel the 73.4% energy return when you push hard, and the plate works in its optimal range. At this pace, few shoes on the market can compete.

On easy runs (5:30/km or slower), though, the shoe loses its point: the plate needs cadence, and you cannot tap into its energy potential. Don't bother taking it out for a recovery run.

How it stacks up against direct rivals

Vs Nike Vaporfly 4 (€290, 195 g, 8 mm drop): the Vaporfly 4 remains the benchmark in the category and is 20 g lighter. The Cloudboom Strike LS is more stable and offers a one-of-a-kind upper experience. A very close match that comes down to personal feel and which brand you prefer.

Vs Adidas Adios Pro Evo 3 (limited elite edition): the Adios Pro Evo 3 is lighter still (138 g), but it is a disposable shoe designed for 1-2 elite marathons. The Cloudboom Strike LS is more durable and can handle several races over a season.

Vs Asics Metaspeed Sky Tokyo (€270, 184 g, 5 mm drop): the Metaspeed Sky Tokyo is built for stride runners (who go faster by lengthening their stride). The Cloudboom Strike LS is more versatile and suits stride runners and high-cadence runners alike. Asics wins on price (€60 less).

Vs Saucony Endorphin Pro 5 (€270, 217 g, 8 mm drop): very similar weights, different philosophies. The Endorphin Pro 5 is more affordable and more stable. The Cloudboom Strike LS brings the groundbreaking LightSpray upper and superior energy return.

© On Running, official photo used for editorial purposes

How to fit it into your RunMorph training plan

The Cloudboom Strike LS is strictly a racing and race-simulation shoe. Here is how I use it when programming RunMorph plans:

Goal races: 10 km, half marathon, marathon. This is the shoe's main job. For an ambitious time goal (sub-2:45 marathon, sub-1:20 half, sub-37 for 10 km), the €330 investment is partly justified by the performance gains and the durability of the Helion HF foam.

Marathon simulation session (1 to 2 per cycle). Once or twice during a marathon build, run 25 to 30 km at goal pace in the LS. You break in the shoe, check how your legs feel after 2 hours and rehearse the race in your head.

Race-specific quality session (60 to 90 minutes). Blocks like 3 x 20 min at half marathon pace, 6 x 1000 m at 10 km pace and so on. The carbon plate is in its element, the foam responds well and you get comfortable at goal pace.

What I do not recommend with this shoe: anything other than racing and race simulation. Easy runs, short intervals, slow long runs: you waste its potential and wear out the Helion HF foam early, and it is not built for high mileage.

RunMorph coach's verdict

The On Cloudboom Strike LS breaks new ground with its upper (robot-sprayed LightSpray) and sits at the top of the market for feel and energy return. The Helion HF + Speedboard + Bounceboard package works as a coherent whole from the ground to the upper, and you can feel it. Hellen Obiri knew what she was doing.

My two reservations: the €330 price remains very elitist and out of reach for most amateur runners (the Endorphin Pro 5 or the Metaspeed Sky Tokyo at €270 offer much better value for money), and the durability of the LightSpray upper over 5 to 10 marathons is still unproven (real-world feedback is too recent).

If you are chasing an ambitious time and budget is no obstacle, the Cloudboom Strike LS is one of the best shoes in the world right now. Everyone else should look at the Endorphin Pro 5, the Metaspeed Sky Tokyo, the Vaporfly 4 or the Kiprun Kipstorm Elite.

Key takeaways for your training

• Elite super shoe with a robot-sprayed LightSpray upper: 215 g, 4 mm drop, 39.5/35.5 stack, supercritical Helion HF foam + Bounceboard, Speedboard carbon plate, 30 g laceless LightSpray upper.
• Who it suits: elite or highly ambitious runners, sub-2:45 marathon, sub-1:20 half, sub-37 for 10 km, fans of On innovation.
• Strengths: 73.4% energy return (world-class), groundbreaking seamless LightSpray upper, one-of-a-kind slipper-like feel, spoon-shaped Speedboard propulsion.
• Limitations: very elitist price (€330), LightSpray upper durability still unproven, only worth it at a hard effort (faster than 4:00/km).
• Matching RunMorph plans: goal race (10 km, half marathon, marathon), race simulation, race-specific quality session.

© On Running, official photo used for editorial purposes