Flanger FP-06 Magnetic Soundhole Pickup Transducer Adjustable Tone Volume Wooden for 39"/40"/41"/42"Acoustic Guitar Made of wooden, soundhole pickup for 39 inch Magnetic transducer captures vibrations quickly. Adjust tone and volume as you like. 6.3mm female converter converts mechanical vibrations to an electrical signal. Passive design, without need for external power. No need for drilling hole, easy to install. Comes with a piece of plastic to fix cable on guitar.