Can be used for rabbits, guinea pigs, any small animal that likes running through tunnels. There are additional pieces you can add to it such as a run or hay rack. I used it to attach two cages together to give my guinea pigs more space. I’ve since gotten a bigger cage for them and no longer need this tunnel set. This is the link to their website:
https://www.omlet.us/shop/rabbit_products/zippi_rabbit_tunnel_system_and_burrow_pipe/