Castelli Fast Feet 4 Socks White, Size S/M

Castelli

There are lots of so-called aero socks out there. But the Castelli Fast Feet 4 Sock has the development and testing to back up the claim. The few socks that have been tested have probably been tested with a static, nonmoving test because it's easier. But a foot is always in motion, so they created a jig that replicates the movement of the lower leg. And they tested it on actual riders to verify the results. This sock can save 2 watts at 50 km/h. The newest version has an updated cuff fit for more comfort and aerodynamic gains. Features Castelli's Fast Feet project — for maximum aerodynamics. Foot portion based on Castelli Rosso Corsa Sock for in-shoe comfort. Polyurethane grip strip at top to keep sock in place. Leg portion constructed with engineered grooved Lycra® to help detach airflow.