The outer cup made of plastic or stainless steel.
The inner have cork to hold flask in the place. Next, in the space between the cups is vacuum, a large vacuuming machine sucks the air from the space between the two cups. And have thin silvered wall of glass between vacuum. At the top has a stopper, stopper made from plastic and it can be pulled upward from the cap for liquid flows through a small hole in the stopper.