Two on offer: Matrix MPU-1 acoustic guitar tuner pickup. features a unique suction cup transducer design for elimination of background noise that can cause interference problems when tuning your instrument, especially in a live environment. In very good condition $8 Matrix universal MPU-2 transducer clips directly onto the bridge and improves tuning signal, eliminating background interference from room noise. 1/4" plug inserts into most tuners. In excellent condition. $12