Just activate in water and the special HyperKewl™ fabric does the rest! These cooling wrist wraps are great because they target bloodflow to have a cooling effect on your entire body. Lower overall body temperature by targeting wrists Hook and loop closure for custom fit Provides 5-10 hours of cooling relief per soaking Lightweight and durable Comfortable, cool mesh polyester outer with HyperKewl™ fabric inner and water repellent nylon inner liner, black poly-cotton trim, and hook and loop attachments One Size - Sold as a PAIR (2 pieces) About HyperKewl» Evaporative Cooling: This simple and effective technology works by combining water with our HyperKewl» Fabric to create garments that gradually release water through evaporation to keep you cool, but comfortable. Typical applications include personal cooling, outdoor safety, industrial safety, construction, emergency services, military, outdoor recreation, athletics, motorcycling and equine.