This is a pack of 3 piezoelectric elements, pre-wired with leads to save you having to solder the leads on yourself. 20mm is a perfect size 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. An electric pick-up is a sure-fire way to take your cigar box guitar or other build to the NEXT LEVEL, and many builders report that their instruments are much more attractive to potential buyers if they include a pickup. So here is your chance to take the plunge without dropping a huge wad of cash! Technical Specs: Plate Diameter: 20mm (.78 inches) Element Diameter: 14mm (.55 inches) Plate Thickness: .42mm (.0165 inches) Lead Length: ~50mm (1.96 inches) Plate Material: Brass Resonant Frequency (kHz): 6.3 +/- .6kHz Resonant Impedence (ohm): 1000 max. Capacitance (nF): 10.0 +/- 30% [1kHz]