A Rudraksha bead is the dried fruit of the rudraksha beads tree. These
beads are strung into rosary (malas) worn by devotees of Shiva. Every
rudraksha bead has 'faces'(mukhi) which differ in number. A rudraksh
bead may have just one face rudraksh to 21 face rudrakshas. Each
number has its own connotation. Rudraksh beads are available in
different faces, each face rudraksha having a valid significance which
includes its reigning God, ruling planet, mantras & the benefits.
http://www.rudrakshabeads.net/