18" - 32" adjustable. The pendant is approx 1" by 0.5".  The mantra "OM MANI PADME HUM" translates "the Jewel is in the lotus", meaning that enlightenment is in the everyday world. The purpose of mantras is to rebirth the self; a refreshment of the self. Mantras are a very powerful way to reduce negative energies and effects. Buddhist do believe that by chanting it may produce a force which will reduce negative karma, accumulate merit, rescue himself from suffering in next life.