Kingtoys Self-adhesive Electronic Acoustic Instrument Pickups Guitar Ukulele Mandolin Banjo Pickup Piezo Transducer Include 3-pack 27mm Piezoelectric Disk Elements+with 2.36" Endpin Jack Fit for most string music instruments such as guitar ,violin ,mandolin etc. To let your acousitc instrument turn into electro-acoustic one Connects to your instrument via 2.36" jack with 23.6" cable. Pre-wired, No Soldering Required High Output - No Battery Required