They are made from rigid plastic and snap together in a modular fashion, so you can have as many or as few as you want in each row. The ones I got are mounted to the ceiling, but that doesn't work in my aviary, so I attached them to a board, then attached the board to the wall.
I haven't had any problem with them falling apart or breaking so far. The birds have not chewed on them and they are easy to clean.
All in all, they are sturdy enough, but probably won't last forever.
If I was so inclined, I might make my own privacy perches, using a dowel and pieces of wood or plastic. I just found it more convenient to purchase a ready-made product. The design is not that difficult to replicate. Just make sure that the top and sides are protected and the perch is short enough that only one bird can fit on each roost.