Piezoelectric Piezo Ceramic 15mm + Aluminum shell

From the shop's description

Description: Piezo elements come in handy when you need to detect vibration or a knock. You can use these for tap or knock sensors pretty easily by reading the voltage on the output. They can also be used for a very small audio transducer such as a buzzer. Resonant Frequency(kHz): 6.3 0.6kHz Resonant Impedance (ohm): 1000 max Capacitance (nF): 10.0 30% [1kHz] Diameter : 15mm