Ergodyne - EGO12331 Chill-Its 6710 Evaporative Cooling Triangle Hat is made with activated acrylic polymers to bring power where you need it most. Soak in water for 2 to 5 minutes to activate. Simply soak again to reuse. A tie closure in the back allows an adjustable, snug fit on a variety of head sizes. This simple, effective and comfortable solution for heat stress prevention is similar to how sweat cools the body. It uses an external water source to draw heat away, helping to regulate body temperature while providing cool relief. When activated, this cooling bandana is comfortable and refreshing for even the hottest days of the year.