Outfitter's Note: this is a UNISEX-sized shoe. Men's sizes are shown — women should order 1.5 sizes below their standard running shoe size. For example: for a women's size 9.5 shoe, order a size 8. Get ready for serious pace in the ultrafast On Cloudboom Strike LS. This futuristic race day shoe delivers On’s lightest, most advanced technology to help you chase finish lines and new PRs. Built with revolutionary LightSpray technology, dual-layer Helion HF foam and a stiff carbon fiber Speedboard®, the Cloudboom Strike LS gives you powerful propulsion at every stride. Details: Upper: The seamless LightSpray construction creates a second-skin fit using a single 1.5 km filament spun by a robot — think of it like 3D printing with thread. At just 30 g, it's On's lightest upper ever, and the laceless design means zero distractions when you're in the zone. Plus, it emits 75% less CO2 than traditional uppers. Midsole: Two layers of over 40% bio-based Helion HF hyperfoam deliver high-speed energy return and impact protection. The pre-shaped carbon fiber Speedboard sits between the layers, transferring every bit of your effort into forward momentum.Outsole: CloudTec elements create faster, smoother transitions, while maximized ground contact gives you the traction to trust your footing when every second counts.