Piezo disc soundboard pickup, 3/4" diameter, attaches to top with double-sided adhesive, wired to a standard 1/4" jack which also mounts on the top or side of the instrument. Easy, straightforward application requiring no permanent alteration of the instrument. Note: if you prefer a permanent internal installation you may place the transducer on the underside of the top and wire it to an endpin jack (not included). K&K Big Shot Transducer Pickup