2. A good thermos cup is generally made of 304 steel inside and outside. This material is better and contains no harmful heavy metals.
3. Observe the internal and external surface quality of the thermos cup. A good thermos cup generally has a smooth surface inside and outside the liner, without scratches or protrusions; At the same time, we should also pay attention to whether the cup mouth is smooth and whether there is a weld.
4. Pour hot water into the thermos cup, wait for 2-3 minutes, and touch the cup surface. If there is obvious temperature rise, it means that the vacuum insulation performance is poor.