stainless steel material‎,‎ alkali‎-resistant and acid‎-resistant‎,‎ not easy to rust‎,‎ longer use life Copper coated reflection layer + mirror surface inner‎,‎ reducing heat loss‎,‎ better temperature preservation Up to 12 hours long‎-acting temperature preservation Mirror surface inner‎,‎ impurities and bacteria are less like to stick on‎,‎ easy to clean High hydrolytic stability material‎,‎ corrosion‎-resistant and durable in use Lightweight and easy to carry‎.‎