The 21oz Standard Flex Cap Flask features Hydro Flask’s unique TempShield™ techonology. Using double wall insulation, the flask protects temperature for hours – keeping cold drinks icy cold and hot drinks piping. The 18/8 pro-grade stainless steel construction protects taste, ensuring there is no flavour transfer from the flask to your drink. Plus the durability of the stainless steel delivers protection against the harshest of conditions. The flask has a proprietary powder coating which is engineered for an easy-grip that is sweat-free, while adding further durability to the flask.