Out there, there are many so-called Aero socks. However, the Castelli Fast Feet 4 sock has the development and test results to prove that it lives up to its name. The few tested socks were likely evaluated with a static test at rest, as this is easier. But since a foot is constantly in motion, we developed a device that simulates the movement of the lower leg. We conducted tests with real cyclists to validate the results. This sock can save 2 watts at 50 km/h. The latest version features an updated cuff fit for more comfort and aerodynamics.

Technical specifications:

• The Fast Feet project by Castelli – for maximum aerodynamics
• The foot part is based on the Castelli Rosso Corsa sock for comfort in the shoe
• Anti-slip polyurethane insert at the top edge to ensure the sock stays in place
• The leg part is made from specially developed ribbed Lycra® to direct airflow.