Even if wind resistance from your shoes only slows you down by half a second every mile, that can cost you whole minutes during a long TT. Better to wear Castelli's Aero Race Shoe Covers from the start and avoid getting behind in the first place. Since seconds really do matter, Castelli designed the Aero Race using computer modeling and wind-tunnel testing to dial in aerodynamic perfection. The testing led to a sleek Lycra panel in the front that gives way to textured mesh further back, the idea being that the texture actually improves airflow by controlling laminar turbulence. A silicone leg gripper at the top provides a smooth seal, and a rear zipper ensures the Aero Race stays snug and streamlined throughout your ride.