Details
Piezo Element with plastic body. Can be used as buzzer along with oscillating circuit. Can also be used as Vibration sensing applications. The plastic body provides resonance when the plate oscillates thus providing louder sound when used as buzzer. For use as vibration sensor the plastic cover can be removed easily.
SpecificationResonance Frequency: 4.6 Khz +/- 0.5 Khz
Resonance Impedance: 200 Ohms
Capacitance: 20nF +/- 30% at 1 Khz
Dimensions- Piezo Plate Diameter: 27 mm
- Piezo Element Diameter: 19.7 mm
- Plate material: Brass
- Element thickness: 0.54 mm
- Plate Thickness: 0.3 mm
- Diamter of plastic body: 30 mm
- Wire Length: 70 mm
For using as buzzer you can drive it as RC oscillation

Many Applications
Searching Piezo Element in google images turns up many interesting applications like Vibration Sensor, Gitar pickup, Earth Quake Sesmometer.
Click here to view result of Google Images
Note: After you receive this product, you need to solder wires to elements like shown below and put the element into plastic cap if your application is buzzer and needs to get sound out of element.