KONG extreme represents the most durable version of the original KONG toy. The ultra-strong, black rubber compound is recommended for power chewers. 1. Perfect for stuffing with KONG treats and Ziggies. 2. Five sizes : Small, Medium, large, X-Large, and XX-Large. 3. Used worldwide by police, drug enforcement, and military K-9 teams 4. Also used by Schutzhund and AKC competition trainers.