Estone&reg; 12PC Piezoelectric Piezos Amplifiers Discs Leads For Cigar Box Guitar Pickups It's suitable for installing in cigar box guitars, foot stompers and other home-made instruments They can also be used for custom pickup arrangements in more traditional stringed and percussion instruments Easy to install, convenient to use Resonant Frequency (kHz): 4.6 +/- 0.5kHz Resonant Impedence (ohm): 300 max