Bionic Rubber is a revolutionary material that can withstand the aggressive play patterns of most pets. Bionic products have been tested in rescue shelters and day cares around the U.S. for years. By making and destroying countless samples, we know Bionic Rubber can hold up to the most aggressive chewers. Throw toy against the spine and it bounces normally. When your dog thinks he knows where its going to bounce, throw it against the opening to create an unpredictable bounce that's hours of fun!