Product Description Brand: Yasuda Stainless Steel Vacuum technology enables to keep liquid hot/cold for longer duration Vacuum insulated flask with copper coating Easy to use Easy to clean Weight: 0.8 kg Colour: Blue warranty: 1 year 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 vacuum flask consists of two flasks, placed one within the other and joined at the neck. The gap between the two flasks is partially evacuated of air, creating a near-vacuum which significantly reduces heat transfer by conduction or convection.Vacuum flasks are used domestically to keep beverages hot or cold for extended periods of time and for many purposes in industry.