The material that we used on the inner layer of our outer shell is PC, therefore, the hardness is pretty high. For the outer layer, we use TPU which has a softer texture so it will neither harm the pets nor make too much noise. Although the Wicked Ball is not strictly a chewing toy, we did test Wicked Ball's resistance to biting, gnawing, and scratching with over 100 dogs and cats. Eventually, Wicked Ball has passed the tests with most of the dogs and all of the cats. Of course, some smart dogs, cats will do everything possible to break the Wicked Ball, but we accept all challenges. Though, if you believe your dog is a heavy chewer, you may stay with your dog the first time that it plays with our Wicked Ball and see how the chewing goes.