"The dog is a rescue, so all I can say is that he is probably mostly American Pit Terrier and a very heavy chewer. He loves this toy and I like it because the plastic protrusions are large enough for me to grasp, twist out of his mouth, and get a good game of fetch going. Its irregular shape makes it bounce erratically, so it's always a surprise to see where it lands. This is the only toy I can actually get out of his mouth to throw. Otherwise, our games of fetch are pretty sorry because I throw, he fetches and won't let go. The I have to wait for him to become desperate enough to share the toy with me befoe I can throw it again."