Evaporative Cooling Skull Cap Evaporative cooling skull cap that is worn around the head and fastened (tied). Great for motorcycle riders, runners, hikers, or just for hanging out Soak in water 1-3 minutes, wring out excess water. The American Flag and Camo caps are 100% cotton and the Black and Royal Blue are 100% nylon outer with a 65/35 polycotton top.