I bought on Amazon the Marshall Playpen 11 panels. I don't see them right now on Amazon but here is a link. Marshall Small Animal PlayPen https://www.amazon.com/dp/B0002ARQT6/ref=cm_sw_r_apan_glt_fabc_HKJC430MR5P38QRXYFW5

Its the one sold by Marshall. it works great! The spacing is nice and small so they cant get out and the bars that are horizontal are spaced far enough apart that they cant climb it. they also sell an extension to it to make it larger. we tried ALOT of "small pet" pens when we were looking but they all managed to have some kind of flaw that our sneaky ferrets managed to find and get out. so i highly recommend this one! here it is on amazon https://www.amazon.com/Marshall-FC-224-Small-Animal-Play/dp/B0002ARQT6/ref=sr_1_2? ie=UTF8&qid=1524961061&sr=8-2&keywords=ferret+marshall+playpen