The upper's GORE-TEX membrane increases breathability while also providing the industry's best water repellency. Where GORE-TEX material is not available, durable hard rubber keeps everything else the same. The same hard rubber wraps the big toe for overprotection and uses thick V-shaped lugs on the sticky outsole for maximum grip and propulsion. Flexible ankle cuffs keep unwanted debris out, while reflective design elements on the heel and lace overlays aid visibility at night. The secret sauce is in the comfortable React midsole, and a carbon fiber plate drawn from the cutting-edge Vaporfly 4% runs the length of the shoe for added stiffness for added stamina while protecting you from hard, uneven surfaces harm.