Heavy-duty storage boxes are ideal for stacking with or without shelving and are designed for maximum stackability. Sturdy corrugated construction delivers lasting box strength. Average amount of evenly distributed weight that can be safely stacked on top of a box is 700 lb. String-and-button closure keeps letter-size files secure. Storage box contains a high percentage of recycled material. Business Source Heavy Duty Letter Size Storage Box 12 / Carton (Quantity)