Simple, easy-to-use tuner that is perfect for the beginning student and parent. Mechanical needle accurately indicates pitch of open string whether plucked or bowed. Pitch is detected through the use of a transducer (included) that directly clips onto instrument?s bridge. Tunes violin EADG strings and viola/cello ADGC strings. Requires one 9V battery. Size 3" x 4 1/4" x 1/2".