The material that we used on the inner layer of our outer shell is PC, therefore, the hardness is relatively high. For the outer layer, we use TPU, therefore, relatively soft but also has a protective effect on pets. We have tested Wicked Ball on more than 100 dogs and cats to test all aspects of biting, gnawing and scratching. Eventually, Wicked Ball has passed the tests (for heavy chewer, bite marks may occur). Of course, some smart dogs, cats will do everything possible to break a Wicked Ball, but we accept all challenges. One tip here, you may wish to stay with your dog the first time that your dog plays with our Wicked Ball and see how it goes.