The NEW Sidi T4 AIR Carbon triathlon cycle shoes features a super-perforated triathlon-specific upper for maximum drainage and ventilation, with a plush, brushed interior for sock-free comfort for fast transitions and supreme comfort on the bike leg. Like all SIDI carbon soles, the Twelve Carbon/Composite sole is made with two different materials blended together, nylon and carbon fibre. It is made out of injected Carbon Fiber in a matrix of Nylon. The Nylon used doesn’t absorb water and doesn’t lose rigidity in hot or humid weather or as it ages. The result is a significantly lighter and stiffer sole Translation: The T4 gives you legs on the bike, and saves your legs for the run.