Thermos plastic cover or cork cover

The cork is good, because the cork can not only expand after being immersed in water, but also achieve better sealing effect, and the texture is loose and the heat insulation is good (the void reduces the heat radiation, convection and conduction). If the plastic plug is empty inside, the air inside is easy to convect heat; if the interior is not empty, it is easy to conduct heat dissipation and plastic smell. Short-term use, generally does not affect health, because plastics that can be used in food or tableware are treated.