We have a new puppy. We got one of those wire pens for him. Unfortunately, he almost immediately figured out he could climb the cross wires! He was out in a flash. SO we got this pen. It is almost perfect. It will be perfect when we get done. The bars are in general about two inches wide. Those he cannot get through. But the gate is a different matter. The bars around the hinge and latch areas are about a half inch wider--probably to accommodate the mechanics of the gate latch and hinge. But that is just enough wider that our puppy can get his shoulders through. Maybe the rest of his body, but we intervened.
This thing is great. I have it set up as a wall spliting my living room in half basically. The panels are sturdy so hold up great when my daughter pulls herself up standing against them. As i have it set up as a wall i did anchor it to the room walls byattaching some Velcro to the room wall with a screw at either end then wrapping the Velcro around a piece of each end section. This has allowed me to create a baby safe area with all her toys and then an adult safe area with no toys to trip over, and itlet meget away with not baby proofing the entertainment center.