I had this product for less than a month. After extended use a crease appeared and then turned into a crack which eventually leaks. I suppose it is quite stressful knowing that you use a stress ball so much it breaks.... ^^.
Anyway, it was good while it lasted.
It is filled with gluey, doughy stuff, so there is a hard plastic thing underneath the face to cover the filling hole I presume.
To get an idea of how it feels: when you press it, it slowly morphs back into it's original shape unlike the foam ones which go straight back; and it doesn't bounce at all.
Having know what it is like, I would have rather have bought the 'Stretchy Stress Fruit: Banana' from Play.com also.
Search for it now. Type in 'Stress Fruit', into the search...