Made of copper, high temperature resistant, stable, durable and long service life Piezo pickups have a diameter of 27 mm. Simple and easy to use. These pre-wired piezo pickups can be easily installed in cigar box guitars, foot pedals, and other homemade instruments for sound and vibration detection Suitable for use in electronic drum triggers, buzzers, DIY pressure microphones, watches, cameras, mobile phones, electronic toys, computers, and other applications Size: Copper sheet diameter 27 mm Material: Copper Color: Gold Package Contents: 15 x Acoustic Pickup Note: Light reflection and different displays may cause the color of the item in the picture to appear slightly different from the actual item. Measurement may vary by +/- 1-3 cm.