Simply soak the MiraCool Headband in cold water for 30 minutes. The MiraCool crystals absorb up to 1,000 times their weight in water, staying hydrated for several days. The crystals work in combination with natural evaporation to release cooling sensations that pass to pulse points and are then carried throughout the body. The 100% cotton MiraCool Headband is washable and reusable. Headband is ideal for cooling pulse points around the head.