These boxes are large sized and can easily fit two pair of women’s shoes you want to double up.  The front and ventilated back are hard plastic.  The sides are thick plastic but somewhat flexible.  Once the box is assembled, it is very sturdy, holds its shape and stacks very well.  I went four boxes high and the stack was secure.  The front door opens and closes easily.  When you are assembling, bend the sides the opposite way and then back the right way and that makes it easier to align and put the back and front on.  I would purchase these again.