Hamster balls can be purchased from your local pet store(s) and are made of clear plastic. They can be taken apart so that you may place your hamster inside of it and then your little hamster can run around. While a hamster ball is very cute and it looks entertaining to your hamster it is actually not a the best of toys for them.
When contained inside your hamster can become frightened of being enclosed or trapped. This could make your hamster panic. Even though the balls have holes for air ventilation, the holes are very tiny and could quite possible not provide your hamster with enough air while inside of them and also it could heat up inside. These toys have the potential to be more cruel than they are entertaining and fun for your pet. Please think of your pet and their safety!
One toy I highly recommend is the tunnels or tubes for your hamsters enjoyment. To be safe make sure the tubes are wide enough and allow enough space to play comfortably. They need to be at least 2 inches in diameter. Make sure as well that they are not too long, this will ensure that the hamster has the proper amount of ventilation that is needed. You also do not have to spend a large amount on expensive, colorful tubing from your pet store. You can make a simple tube out of pvc pipe (read this guide here), however check the ends and make sure they are smooth. Paper towel inner cardboard rolls can also be fun for your pet.