Shipping boxes come in a variety of shapes, sizes, and strengths for storing and transporting goods. For safe shipping, boxes hold objects wrapped in protective packing or surrounded by void fill material. They can be piled in a warehouse or shipping container after being sealed shut. Shipping boxes come in a variety of strengths, but the most popular are 200# and 32 ECT. Boxes labeled 200# offer better protection against bursting and stackability than boxes designated 32 ECT. Specialty boxes are used to transport hazardous items or to protect objects from extreme heat or cold.