I would not want to 'stuff' the smaller balls as I can only see that leading to a big mess. The larger maze ball I did put dehydrated treats into and I finally saw the pup going after it this morning - cats still not interested in any of them. When I have more time I will try to engage my pup in the smaller balls as well - he loves to chew so I would think they would be the perfect medium to satisfy his craving to masticate...