Bankers Box Stor/File 704 Letter Size Storage Box, Carton of 12. Medium-duty storage boxes are ideal storage for inactive files, working 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 the 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 500 lb.