Castelli Fast Feet 4 Sock

For road racing or when you can't wear a Fast Feet TT Shoecover, this sock saves watts. PRODUCT 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 TECHNICAL FEATURES

Insulation 1/5

Waterproofness 1/5

Windproofness 1/5

Breathability 4/5

Lightness 4/5

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

FAST FEET 4 SOCK There are lots of so-called aero socks out there. But the 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 we created a jig that replicates the movement of the lower leg. And we 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.