The Red Thunder Mountain Longhorn pepper looks like a long, skinny, and curly relative of the Cayenne pepper. The peppers can grow to be over 15 inches in length, but they are thin like Chile de Arbol peppers. The Red Thunder Mountain Longhorn pepper, which averages about 20,000 to 40,000 Scoville Heat Units, was originally grown in the Leigongshan Mountains in China. Peppers are a common ingredient in many regional recipes. Once the pepper is harvested, it is dried out and smoked prior to use.