In summer, put some frozen ice cubes in the thermos bucket, which is a special kind of blue liquid, so that the food is not easy to go bad.

If the weather is cold in autumn and winter, put a lock cup in the heat preservation barrel, with boiling water in it and a towel around it, so as to keep a little temperature. Of course, if the weather is fine in go on road trip, you can put the lunch box on the black platform above the dashboard and keep warm in the sun.