I just bought my second one, and combine the two, to have a larger pen.  They're sturdy enough to be durable over time, yet lightweight enough that it's very easy to carry and move them around.  Lack of a door is not an issue, since you can just swivel an end panel open, just like a door.  And if your pet is little, you can just lean over the side and pick them up.  For the money, these are really a great deal!