Guitar Pickup Piezo Clip On Transducer For Guitar Violin Ukulele Mandolin This pick-up will work with the majority of Tuners/Amplifiers/Speakers that have a jack input of 6.0mm. This brand new pickup is designed for clipping in the sound hole of your acoustic guitar. Used for tuning or amplifying strings intruments The pick-up works with a wide variety of instruments, and is essential for tuning up in noisy surroundings as it clips to the body of your instrument and picks up just vibrations as opposed to the sounds transmitted in the air. Jack:  6.0mm