Brass and Copper with Mantra on outside of Cylinder as well.
A prayer wheel is a cylindrical wheel (Tibetan: འཁོར་ལོ།, Wylie: khor lo) on a spindle made from metal, wood, stone, leather or coarse cotton. Traditionally, the mantra Om Mani Padme Hum is written in Newari language of Nepal, 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, but other mantras may be used as well. According to the Tibetan Buddhist tradition based on the lineage texts regarding prayer wheels, spinning such a wheel will have much the same meritorious effect as orally reciting the prayers.