vacuum flask, also known as vacuum mug, thermos or insulation cup, tumbler, water bottle in English,

a type of container specifically designed to keep beverages hot or cold for extended periods. It typically consists of two or more layers of material with a vacuum space between them, which minimizes heat transfer by conduction or convection. The inner layer is usually made of glass or metal, such as stainless steel, which is effective in retaining heat, while the outer layer provides insulation and protection.

The vacuum flask’s design includes a stopper or lid to prevent heat loss through evaporation and to allow for easy drinking. Some modern designs also incorporate additional features like leak-proof seals, handles for easy carrying, and even built-in tea infusers or filters.

These flasks are popular for outdoor activities, commuting, or simply enjoying a hot beverage throughout the day without the need for reheating. They are versatile, durable, and an essential item for those who appreciate their drinks at the desired temperature anytime, anywhere.