A vacuum flask (also known as a Dewar flask, Dewar bottle or thermos) is an insulating storage vessel that greatly lengthens the time over which its contents remain hotter or cooler than the flask's surroundings. Invented by Sir James Dewar in 1892, the vacuumA sports bottle is a water tool for outdoor sports. Compared with other water tools, a sports bottle has the characteristics of durability, safety, reliability, convenience and insurance. Sport water bottle has become a relatively popular and environmentally friendlyA mug is a type of cup typically used for drinking hot drinks, such as coffee, hot chocolate, or tea. Mugs usually have handles and hold a larger amount of fluid than other types of cup. Travel mugs (introduced in the 1980s) generally employ thermal insulation properties for transporting hot or cold liquids. Similar to a vacuum flask, a travel mug is usually well-insulated and completely enclosed
Glass water bottles are heavier than plastic, stainless steel, or aluminium, and are easier to damage or completely break. Like metal, they also have a high level of temperature transfer, so they are not ideal for very hot or cold liquids. Some types of vacuum-insulated flasks use an inner layer of glass (which is easy to clean), and an outer layer of metal or plastic which helps shield the glass from breakage. Such bottles may still break if dropped, and thus some brands are triple-layer, with the glass inside two layers of plastic; this is a common configuration for large flasks intended for coffee or other liquids that need to be insulated. Stainless steel water bottles are growing in popularity, they are durable, and their previous contents retain less odor and taste than most plastic bottles, but can sometimes develop a metallic taste. Therefore, stainless steel bottles often contain resin or epoxy liners to protect the contents from taste and odor transfer or corrosion. Although most liners today are BPA-free, older and less expensive models can contain BPA and can also use glass liners. Metal (especially steel) water bottles can be heavier than their plastic counterparts. Single-walled metal bottles readily transfer temperature of contents to external surfaces, which makes them unsuitable for use with unusually hot or cold liquids. Double-walled metal bottles are insulated to keep cold liquids cold and hot liquids hot, without the external surface being too hot or too cold. Because double-walled bottles have more metal in them, they are more expensive. They are typically vacuum-insulated, but some may have a solid or gel insulation between the metal walls.