What Our Gearhead(R) Experts Are Saying:"This shoecover is all about free speed. It fits tight, stays put, and noticeably smooths airflow around the feet. I've used it in both time trials and flat road races-it's easy to get on and off, and it doesn't flap or bunch like cheaper covers."We reach for the Fast Feet 4 TT Shoecover when the goal is pure speed. Part of Castelli's Fast Feet project, this shoecover is wind-tunnel tested and proven to reduce drag across both time trials and high-speed road races. The lower portion uses a silicone-coated fabric to smooth airflow over the shoes, while the upper section is made with grooved Lycra(R) to manage turbulent flow at the ankle. Flat polyurethane tape at the cuff holds everything securely in place, even at race pace, and the clean, contoured fit eliminates wrinkles and flapping. When every watt matters and aerodynamics can't be left to chance, this is the shoecover we trust.