A bare piezoelectric transducer that can be used either as a sensor, or as a speaker.
Good to have a few of these around.
A handy component for all kinds of projects, as they can both produce sound and revive it. Not that all speakers and mics cant, but as far as cheep components go they are rather versatile.
Great as always. No trouble to place order and no problems with it. It was delivered on time just as they said it would. I have ordered here several times and will continue to do so!