PrimaLoft® sport is lightweight, breathable and offers superior water repellency, so you remain dry, warm and comfortable even under the most extreme conditions. It uses a microfiber structure to help the body retain warmth and conserve energy. The PrimaLoft® insulation core creates millions of air spaces suspended in the microfiber mesh. These air spaces are so fine that water drops bead on the surface. Even when forced into the PrimaLoft® core, water is repelled and not absorbed by the microfiber structure, so PrimaLoft® keeps you warm even under wet conditions.