Medium-duty storage boxes are ideal storage for inactive legal-size files and work with or without shelving units. FastFold, one-step setup makes box assembly fast and easy. Maximum security box with string-and-button closure keeps contents secure, even if box is overturned. Stack up to five units high. Average amount of evenly distributed weight that can be safely stacked on top of box is 550 lb. Storage boxes are made with a high percentage of recycled material.