The gel packs are similar to the blue-ice packs you might use for your cooler, with one big difference. This gel freezes and melts at 58°F. Remember that the temperature of a substance stays the same as it changes state. This is an important concept in making air conditioning work. This gel stays at 58°F until all of it has melted, and 58° is comfortable, as opposed to keeping a 0°F gel pack next to your body. Further, you can freeze the removable gel packs in a refrigerator or in a cooler with ice. A couple of users commented that it is important to keep the packs flat during the freezing process. Otherwise, the hard, lumpy gel packs make the vest uncomfortable. Here is a link to learn more about these cooling vests. I must tell you that I have not personally used one – yet. But is certainly sounds like a cool idea.
Here are a few links to learn more about cooling vests.