My puppy has used the pen right up til he was alomost a year old, ans was always happy to go in there. It is better if it is put in a corner of the room, as it could be tipped by a strong dog pushing on it. BUT I just wanted to point out a safety issue I had. Within minutes of putting my 8 week old pup in there for the first time he got his mouth wedged between the bars/mesh, I guess he was biting on it. Fortunately this happened wilst I was not too far away so heard his screams and was able to release him before he was injured. For the rest of it's use I lined the pen with cardboard (and as I was now traumatised as well as the dog his crate was also lined with 'chicken wire') so that it would not be repeated. I am sure that this was not a fault with the product itself but I just wanted to warn you all as I dread to think of the outcome should this have happened whilst I was not close to hand, and particularly if I had been out/in bed.