Extreme Kong's exclusive black natural rubber formula is the world's strongest dog toy rubber! It's now being used by powerful chewers around the world like police K-9 teams, drug enforcement and military K-9 teams, AKC competition trainers, Shutzhund Clubs and more. Puncture resistant Super bouncy, and chewer friendly. Resilient, durabile, and bouncey. Satisfies a dog's natural need to chew Cleans teeth and conditions gums. Thick, flexible walls that keep springing back for more! Non-toxic, nonabrasive, non-splintering, and does not get sharp when chewed. Recommended by veterinarians, trainers, dog professionals and satisfied customers world wide.