Storage boxes feature 1-1/2-end, 1-1/2-side construction for moderate stacking needs in rooms with or without shelving units. Medium-duty boxes with Quick Setup Assembly assemble quickly and are easy to set up. Each box holds letter-size or legal-size files. The deep, locking liftoff lid locks into place for high-security storage you can trust. Smooth-rolled box edges add strength and help prevent paper cuts. Average amount of evenly distributed weight that can be safely stacked on top of box is 550 lb. Each storage box contains a high percentage of recycled material.