In all Buddhist cultures, monks and lay practitioners use prayer beads or rosaries to help them count their prayers and incantations. In Sanskrit they are known as mala or Japa mala. They are usually round, but in some cases, they are carved in the form of human skulls, a reminder of the impermanence of life. Traditionally, Buddhist rosaries have 108 beads, representing the 108 human passions, or one mala counts as 100 mantras, and the 8 extra are meant to be dedicated to all sentient beings (the practice as a whole is dedicated at its end as well). Some smaller Chinese rosaries have 18 beads, one for each lohan. In Pure Land Buddhism, for instance, 27 bead malas are common. In China such malas are named "Shu-Zhu" (”Žì in Japan, "Juzu". These shorter malas are sometimes called 'prostration rosaries', because they are easier to hold when enumerating repeated prostrations.
Even the beads that fasten the string together have a meaning: they symbolize the three jewels of Buddhism: the Buddha, the dharma (his teachings), and the Buddhist community. The string passing through the beads stands for the power of all the Buddhas that runs through everything.
3/8" diameter beads, 19.25" closed-loop length