I packed a few stir-fried dishes from the hotel a few days ago, and found that the dishes were still warm after I got home for a long time. Why can the lunch box be kept warm for so long?

Most lunch boxes on the market adopt shallow design with wide top and narrow bottom, which seems generous, but the capacity is not enough. Our lunch box king adopts vertical deepening design, with almost the same width from top to bottom, sufficient depth and capacity. Although this design has a certain technical test, we still insist on adopting our design concept, which makes our lunch box radiate slowly and plays a good role in heat preservation to some extent.