Shipping boxes, pads and tubes are containers that package products for transit and delivery and protect them from damage during shipping. Boxes come in a variety of sizes to accommodate many types of products. Box strengths vary, but 200# and 32 ECT are common strength ratings for shipping boxes. Boxes labeled 200# provide more protection against bursting and are stronger for stacking than boxes labeled 32 ECT. Mailing tubes hold rolled posters, maps, or drawings for shipping so they don't get bent. Corrugated pads and sheets are paper or plastic that layer between items in a shipment or pallet. Wood crates are stronger than cardboard boxes for shipping large, heavy items such as machines, engines, or metal parts.