Traditionally, the mantra Om Mani Padme Hum written in Sanskrit on the outside of the wheel. Also sometimes depicted are Dakinis, Protectors and very often the 8 auspicious symbols Ashtamangala. At the core of the cylinder is a "Life Tree" often made of wood or metal with certain mantras written on or wrapped around it. Many thousands (or in the case of larger prayer wheels, millions) of mantras are then wrapped around this life tree. The Mantra Om Mani Padme Hum is most commonly used.