The HyperKewl Cooling Sport Vest by TechNiche International was designed with their patented HyperKewl Cooling Fabric for the athlete that wants to stay cool and comfortable during competition. This vest provides 4-10 hours of cooling relief at up to 15F from the ambient temperature. The combination of unique fabrics creates a water management system. The unique HyperKewl Cooling fabric absorbs, stores and releases water within the multi-layered material. Water is released through evaporation, energy is consumed, and a chill effect is created. The HyperKewl Cooling fabric actually cools the body exactly the same way the body cools itself through evaporation. When the vests are worn over a shirt or uniform - undergarments will remain dry due to the waterproof lining. The vest will start cooling immediately and will stay cool for up to 4-10 hours depending on the airflow. Materials: Comfortable quilted nylon outer with HyperKewlTM fabric inner, water repellent nylon liner and black poly-cotton trim.