There are many so-called "aerodynamic socks" available on the market. But only Castelli Fast Feet 4 socks have been developed and tested to truly deserve this name. The few socks tested were probably evaluated under static conditions, without movement because it’s easier. But the foot is always moving, which is why a model was created to replicate the movement of the lower leg. And we tested it on cyclists to verify the results. With these socks, you can save 2 watts at 50 km/h. The new version features an updated cuff fit for greater comfort and aerodynamic advantage.

• Weight: 48 g
• Temperature: 10°C - 38°C / 50°F - 100°F
• Fit: Race

Product Features:

Fast Feet Castelli Project: for maximum aerodynamics

The foot part is inspired by the Castelli Rosso Corsa Sock for maximum comfort inside the shoe

Polyurethane anti-slip strip at the top to keep the sock in place

The leg part is made of Lycra® with engineered grooves to promote air circulation