Why is the water in this thermos still so hot after a day? What is this?

The inner container of thermos bottle is made of glass, the cork is cork, and both glass and wood are poor conductors of heat. 2. There are bright electroplating layers inside and outside the thermos bottle, which should be placed on the bottle wall as far as possible to absorb and dissipate the heat stored inside. 3. The bottle liner is double-layered, with a vacuum in the middle, which removes the air between the two layers of the bottle liner, effectively preventing the way of air heat transfer.