Castelli

Fast Feet 4 Sock

What Our Gearhead® Experts Are Saying:

"I’ve tested a lot of aero socks, and the Fast Feet 4 is one of the few that stays in place and delivers noticeable performance. The grooved texture makes a difference in airflow, and the bottom feels like my favorite training socks—just faster."

The Fast Feet 4 Sock is the result of Castelli’s aerodynamic obsession, designed for riders chasing marginal gains and podium seconds. Developed under the brand’s Fast Feet project, this sock combines an aero-tuned cuff with a comfort-driven footbed to deliver pro-level performance without compromise.

The upper portion features engineered Lycra® with vertical grooves that help manage airflow, detaching it cleanly from the leg to reduce drag at one of the most exposed points of the rider’s silhouette. A polyurethane grip strip holds the sock securely in place, even under high cadence and high power. Meanwhile, the foot portion mirrors Castelli’s Rosso Corsa sock—offering moisture control, light padding, and arch support where it counts.

Optimized for time trials, crits, and race-day speed, the Fast Feet 4 Sock helps you get the most out of every pedal stroke.