This stainless steel lunch box usually can keep food warm or cold for about 2 hours with the your extra insulated lunch bag. The stacking design you could freely combine them into 3 layers lunch box to facilitate the storage of different amounts of food. Free combination of layers, easy to carry. It's not only for lunch box container but also can be used as cooler bag suit for necessity to gym, picnic and other outdoor actives where you want to eat your own delicious food. It is perfect for student, office worker, outdoor work etc.