I bought a few years ago for my violin, it's not terrible, unless you thoroughly equalizer signal. is not a true micro piezo is the sound of an o rather nasal.

you should rather look at the micro AudioTechnica ATM35 is a true condenser microphone, and therefore consquent, placing it well, will give a much better sound than piezo. now is the one I use for the violin, it is convenient (very small micro system mounted on a gooseneck + clip to attach the mentoniere)