Actually made of metal and hasn't rusted yet after a few months. I use the pen as a barrade between my fence and house, easily used for that purpose or a pen. Comes with long spikes to drive into the ground to hold in place; the spikes are also the hinge pins between the pieces so you can angle each panel as you see fit for your purpose. Since the hinges are spikes...I don't suggest using this pen inside or on a hard surface.