I have got one very similiar to this, if you are using it with other buns close to each other, be warned some buns will jump out of it!! Not good if you have unneutered females and males about!
I dont use mine for smaller buns if the mesh on them is big, you can keep your eyes open for one with finer mesh, I have a small meshed one I use for pairing up which 3 week old babies will not escape from, it is only 6 panels though.