Twice the protection of a standard carton. Heavy duty construction provides greater protection and stacking strength. Industry Standard Double Wall Corrugated. Double-wall boxes provide maximum stacking strength. 275# Double-wall/ECT-48 (Edge Crush Test) - holds up to 100 lbs. Heavy-Duty boxes provide added protection to ensure that your shipments arrive safe. Contains a minimum of 30% recycled content. Recycled Content. They are made with a minimum of 30 percent recycled content, so you can feel good about buying them. Heavy Capacity. Specially crafted to reduce the incidence of customer returns due to damage, these boxes feature a double-walled design that makes them resistant to crushing and puncturing, so your items arrive in tip-top shape.