men's vests for layering with shirts -Booster Cooling Pack Set - for use with Sports, Classic, Concealable, and High-Visibility Cool Vest | "Explore Stylish and Comfortable Hoodies, Sweatshirts, Jackets, Polo Shirts & More!"

Booster packs have a lower freezing point and 50 percent more cooling capacity than the small packs included in our standard set of adult cooling packs. The booster packs are designed to be paired with the standard large packs to extend the period of cooling comfort by 45 minutes or more. Because it replaces the standard small pack, there's no additional weight. The booster packs feature horizontal cells that conform to your torso as you bend and stretch. The set consists of four small packs that weigh 7 ounces each. Because of their lower freezing point, they must be charged in a freezer. Standard packs may be charged in a freezer, refrigerator or ice water. Once all the packs are solid, slide one of the standard four-cell packs into each pocket of the vest. Then slide one of the three-cell booster packs in each pocket, on the outer side of the four-cell pack. You want the four-cell packs closer to your body; they hold a comfortable temperature of around 59 degrees F. The green booster packs are much colder; they're designed to keep the inner packs cool, but not cold, for longer periods.