It is the metal pen that is either 3 or 4 foot tall (we have a 4 foot one, I don't want any climbing out!) and then is in sections that fold down or fold out and then you can make a pen the shape that you want. You get them at Petsmart or Petco. It's hard to explain, but here is a pix of our boyz in the Xpen this summer on the river. We bought 2 of them and put them together to make a bigger play area
__________________  Rex & Rowdy's Mom  |