The Wave Sky 5 offers a lighter weight and better fit, thanks to its woven upper, as well as better energy return, thanks to Mizuno Enerzy Core, Mizuno's most responsive material to date. Plus, it's made from recycled materials and designed for more enjoyable runs. Mizuno Enerzy Core technology offers the most resilience and flexibility. Mizuno Enerzy (foam) technology offers versatility in its application, while maintaining softness and resiliency. It allows for enhanced performance capabilities. Mizuno Wave Technology (plate-like) disperses impact energy over a wider area, providing a stable platform and superior cushioning. X10 outsole: This is a durable carbon rubber outsole that allows for longer wear. Stretch fabric upper. Weight (size 9): 309 g (10.9 oz).