Piezo buzzers are used for making beeps, tones and alerts. This one is petite but loud! Drive it with a 3-30V peak-to-peak square wave. To use, connect one pin to ground (either one) and the other pin to a square wave out from a timer or microcontroller. For the loudest tones, stay around 4 KHz, but works quite well from 2KHz to 10KHz. For extra loudness, you can connect both pins to a microcontroller and swap which pin is high or low (\’differential drive\’) for double the volume. Datasheet available here. Specification Diameter: 11.90mm/0.47in Height: 6.53mm/0.26in Weight: 0.70g/0.02oz