I am using them to organize my current & previous year's income tax records. We itemize but I am still going to be able to fit more than one year in a box. Their size and shape allow them to store neatly on a shelf.
The size worked well - having a "bad" back meant not overloading boxes. The size was large enough to get several items packed but not too big that you felt you would overload it so as not to waste the space inside.