Shipping boxes come in many shapes, sizes, and strengths to contain and protect products for storage or transport. Boxes hold items wrapped with protective packaging or surrounded with void fill material for safe shipment. They can be sealed closed and stacked in a warehouse or shipping container. Box strengths vary, but 200# and 32 ECT are both common strength ratings for shipping boxes. Boxes labeled 200# provide more protection against bursting and are stronger for stacking than boxes labeled 32 ECT. Some specialty boxes ship hazardous materials or insulate products from excessive heat or cold.