Our little ratty friends have out grown their small play pen which was only 12" high so we had to get another one.
We decided to go with one that is a lot higher but once we put our buddies in the play pen the were able to climb up the verticle wire sides and get out so we had to cut some plastic from a shower curtain and clip that to the very top of the pen having a few inches hang over the inside of the pen which stopped them from getting out.

It was funny to watch them climb up the verticle wires on the cage and the truth is I never thought they were able to do it but no sooner than we setup the pen and put our pet rats in the pen Myles started climbing up the sides. He got up about half way and then slid back down but after a few attemps he made it to the top and started walking his way over to Jennifer on the very top horizonal wire so I had some plastic left over from making a bottom piece so the pee would not get on our carpet so I cut some pieces to fit over the sides and clipped them on with some heavy duty clips. We drapped the plastic over the insides of the pen so when they made it toward the top they could not grab onto the top and get out which worked just fine.
They tried for about a half hour to excape and finally gave up and wanted to sleep so we put them back into their cage so they could sleep.
Having this play pen will allow them to get some good exercise when they try to climb up the sides and they are determined to excape but hopefully the plastic we clipped on the top of the cage will stop that and I hope they do not give up since its great exercise.
Its funny to watch them get toward the top and then slid down the wires to the floor.
The pen we got is "MidWest Small Animal Exercise PlayPen with 8-panels - 29" height by 18" width which is pretty large area to play in and at this time its a little large for our little rats but when they become adults it will be just the right size and hopefully the will not excape.
If you want to learn more about this Play Pen just click here.