Originally Posted by http://tour-de-france.velonews.com/article/80922/how-garmin-chipotle-keeps-its-riders-fresh-for-the-tour

On the bike the team uses a custom made item the riders have bestowed with many names. For our purposes, we’ll call it an Ice Sock. The team has hundreds of these tubes made from a soft poly-fiber. On hot stages the Ice Socks are filled with ice and passed out with extra bottles when the riders come back to the team car. The socks, stuffed around the shoulders and neck, keep the riders cool through the properties of conduction, evaporation and convection.

“If you use something like this,” says Lim. “You’re getting the evaporation; you’re getting the conduction and the convection because you’re riding through air. If you use plastic [and the reason we don’t is] you hold onto the weight of the water; the bag stays full.”