Your body heat and surrounding temperature will slowly make the water inside the vest vaporize. This causes the surface of your skin to cool down before you get all sweaty. Depending on the temperature and humidity, a 500ml fill will last up to 3 days. Good news for riders with a back pack: the filling cap has evolved into a special waterproof zipper construction at the back.
Lining: Nylon jersey.
Other Specs: 50% PU, 50% Ultra Fresh material with Anti bacterial treatment.