Updated for better fit and feel when fully hydrated. 100% nylon vest with embedded HyperKewl lining. Lining absorbs and holds water that slowly evaporates in higher temperatures to provide a cooling effect. Vest is fully hydrated when soaked for 1-2 minutes. Zipper front. Stretch side panels. Embroidered graphics on left chest. Polyacrylite crystals last approximately one year or fifty uses. Rubber badge on left chest.