Zan Headgear 3-In-1 Headwear BDC007 3-in-1 Head & Neck Cooler, 100% Cotton, Olive Drab, Solid 100% cotton bandana with cooling crystals. Provides hours of cooling relief. Reusable, non-toxic cooling crystals are activated by wetting the bandana with water. One size fits most. Keeps you cool. Ideal for use under your helmet.