1 oz,3 oz The Chili de árbol is a small and potent Mexican chili pepper, also known as bird's beak chile and rat's tail chile. This chili is related to the cayenne,and has a rich red color and a thin flesh., but Its intense heatis slightly less than that of cayenne peppers. De Arbol's are rated between 15,000 and 30,000 Scoville units, and 7- 8 out of 10 in heat scale.