The microwave lunch box made of PP (plastic polypropylene) is the only plastic box that can be put into the microwave oven, and can be reused after careful cleaning. It should be noted that some microwave lunch boxes are indeed made of No.5 PP, but the lid is made of No.0 PE/kloc-0. Because PE is not resistant to high temperature, it can't be put in the microwave oven with the box. To be on the safe side, open the lid before putting the container in the microwave oven.