316 Stainless Steel Liner Vacuum Insulated All-Steel Thermos Flask This thermos flask combines practicality and safety. Its inner liner is made of 316 stainless steel, featuring corrosion resistance, easy cleaning, and high hygiene. With vacuum insulation technology, it achieves long-lasting heat and cold retention—some models can keep liquids hot or cold for over 24 hours. The all-steel outer shell is sturdy and durable, paired with an airtight lid to prevent leakage. It comes in various designs, including large-capacity versions for outdoor and home use, and compact, portable ones for daily commuting, meeting drinking needs in different scenarios.