A thermos flask is mainly composed of inner pot, outer shell, sealing ring and cup cover. The inner pot uses 304 stainless steel, which has good thermal insulation properties. It can keep the water temperature well and avoid affecting the taste due to temperature decrease. Besides, its insulation effect is also suitable for cold drinks. Using a thermos flask not only can reduce the number of disposable cups used, but also reduce energy consumption. It has a simple structure and is easy to clean, so it will not breed bacteria and odor. It is not only easy to carry but also very lightweight. Having a cup of hot chocolate or a sip of cold drinks during lunchtime or when traveling is a great choice, avoiding the economic burden of purchasing expensive outdoor drinks.