A crunchy, oat based cereal, shaped like tiny donuts. They come in several flavors, such as
3. apple cinammon
4. honey nut
5. graham cracker
They are good for your heart, because the oat fiber is microsoluable and "scrubs" cholesteral from your circulatory system.
Hamsters and ferrets love Cheerios; they are a good training device. I love them too.
The ferret digestive system is purely carnivorous, so don't let them fill up on carb based foods, even ones that are healthy for us, like Cheerios.