Zwilling Thermo Thermos Flask 0.42 L is made of 18/10 stainless steel and BPA-free plastic, which keeps your coffee or tea warm for up to seven hours or your cold drinks chilled for up to ten hours. The thermos flask has an integrated removable tea strainer in stainless steel and a rubber bottom that makes it stable on the ground. The lid is tightly sealed, allowing the thermos flask to be safely carried in a bag without leaking.