Cayenne chile peppers are extremely hot and provide the heat for many spicy dishes. When fresh, cayenne peppers appear wrinkly and may be either deep green or bright red (when mature). They can range between 5 and 10 inches (12.5–25.5cm) long and are generally about 1/2 to 1 inch (1.2–2.5cm) across. The red, mature pepper is hotter than the green. Cayenne peppers tend to be long and hooked and they terminate in a sharp point.
Cayennes are pungent peppers with heat scores that measure between 30,000 and 50,000 Scoville heat units. How high a chile pepper scores on the heat scale is determined by high-performance liquid chromatography measurement of how many parts per million capsaicin it contains. This figure is then converted into the historic Scoville heat units that signify how much dilution is necessary to drown out the chile’s heat. The heat level of a chile is given as a range because it varies with how and where the pepper was grown and how mature it is.