CASTELLI Fast Feet 4 Sock

$78.99

Aerodynamic cycling socks that reduce drag with a secure, breathable fit for race-day performance.

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White

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Free standard shipping Canada-wide over $100

30-day returns on eligible unused items

Ships from Guelph, Ontario

Decision guidance

Is this right for you?

Best For

Road racing, time trials, criteriums, and high-speed competitive cycling where aerodynamic efficiency is critical.

What to Know

Compression-style race fit with a secure silicone grip cuff and low-bulk foot section for comfort inside performance road cycling shoes.

Why We'd Choose It

Choose the Fast Feet 4 Sock for its proven aerodynamic benefits validated by dynamic testing and real rider trials, combined with breathable materials and a stable fit that supports high-speed performance.

At a glance

Product facts

Fit: Race fit
Conditions: 10°C - 38°C (50°F - 100°F)
Use: Road cycling, time trials, criteriums, endurance racing
Key feature: Grooved Lycra® aero fabric with silicone cuff for secure fit

Product Story

Product details

Performance and Aerodynamics

The Castelli Fast Feet 4 Sock is designed for elite-level aerodynamic performance in road racing, time trials, and high-speed cycling. Developed through rigorous aerodynamic testing, including dynamic simulations replicating lower leg movement, these socks reduce drag and save up to 2 watts at 50 km/h.

Aerodynamic Construction

The sock features an extended aero leg section made from engineered grooved Lycra® fabric to smooth airflow and minimize drag. The close anatomical fit reduces wrinkles and excess material for consistent aerodynamic efficiency.

Fit and Stability

A polyurethane silicone grip strip at the top keeps the sock securely in place during aggressive riding. The foot portion is based on the Castelli Rosso Corsa Sock, providing low bulk and comfort inside road cycling shoes.

Breathability and Comfort

Despite its aerodynamic focus, the sock uses lightweight, breathable fabrics that manage moisture effectively during high-output efforts. The stretch fabric allows unrestricted movement with a compression-style race fit.

Intended Use

Ideal for competitive cyclists seeking marginal gains in road races, criteriums, time trials, and fast endurance rides.

Key Specs

Specs

Weight	50 g Lightweight construction for performance cycling
Temperature Range	10°C - 38°C / 50°F - 100°F Suitable for warm to moderate conditions
Fit	Race fit with silicone grip cuff Compression-style fit optimized for aerodynamic performance
Material	Engineered grooved Lycra® leg fabric, low-bulk foot section Optimized for airflow and comfort

Questions & answers

Common questions

What makes the Fast Feet 4 Sock aerodynamic?

The sock uses engineered grooved Lycra® fabric on the leg to smooth airflow and reduce drag, validated by dynamic testing replicating lower leg movement and real rider trials.

How does the sock stay in place during riding?

A polyurethane silicone grip strip at the top of the sock keeps it securely in place under race conditions.

Is the sock comfortable for long rides?

Yes, the foot portion is based on the Castelli Rosso Corsa Sock, providing low bulk and comfort inside road cycling shoes, with breathable fabrics managing moisture effectively.