Andoer KQ-1A Piezo Contact Sound Hole Guitar Pickup Transducer 6.5mm Male Plug 3m Audio Cable for 38"/39"/40"/41" Acoustic Guitar Piezo pickup is sensitive enough to capture vibrations quickly and convert mechanical vibrations to an electrical signal. Arc-shaped design, easy to inlay along edge of sound hole stably. Cable with 6.5mm male plug, approx.3 meters in length, connecting pickup to amplifier. Passive design, without need for external power. Design for 38"/39"/40"/41" acoustic guitar.