Exercise is very important to your pet in order to keep him fit and healthy. The habitrail mini fly wheel hangs from the top of your pet's cage and is adjustable to different heights making it ideal for many different cage designs. The habitrail mini fly wheel is designed specifically for mice and dwarf hamsters. It even has two round hubs that make it feel like someone is petting their back as they're running. Talk about taking good care of your little pal.