The principle of the thermos cup is that it has a two-layer structure with a high vacuum state in the middle, which can block convection and heat dissipation. At the same time, the added mirror function in the bottle can effectively block the heat loss due to radiation, so that the liquid in the cup can maintain a certain temperature.

①Tightness: Fill the cup with water, tighten the lid, and turn it upside down. If the cup does not leak, it proves that the cup is well sealed.

②Insulation performance: Pour boiling water into the cup, tighten the lid and leave it for a few minutes, and then touch the body of the cup with your hands. If the body of the cup is hot, especially the bottom of the cup, it means that the cup’s insulation performance is not good.

③Quality of accessories: Observe the appearance and accessories of the cup. If the body and inner container of the cup are smooth, without burrs and scratches, and the plastic accessories have no peculiar smell, the quality is good.

④Material identification: 18/8 of the cup body indicates that this stainless steel material contains 18% chromium and 8% nickel. The material that meets this standard is a green product that meets the national food-grade standard, and the product is rust-proof and corrosion-resistant.