plastic stopper.
Outer plastic or stainless steel case.
Outer layer of glass coated with reflective material (or stainless steel in unbreakable flasks).
Vacuum.
Inner layer of glass (or stainless steel in unbreakable flasks).
Additional insulation reduces heat losses and cushions flask against impacts.
Add the top has a stopper, stopper made from plastic. It can be pulled upward from the cap for liquid flows through a small hole in the stopper
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