1. In the workmanship of the finished product, see if the whole stainless steel hip flask is welded coherently. Don't choose if there are small mistakes.
2. Feel whether the mouth and bottom of the stainless steel hip flask are a bit rough. Don't choose if there is roughness.
3. Pour some water into the stainless steel hip flask and cover the hip flask lid to see if there is any leakage.
4. Learn more about the industry of hip flasks, choose a manufacturer with a good reputation, and check whether the hip flask meets domestic hygiene standards.