Piezo discs are great for constructing pickups for acoustic instruments. Many users love them as the pickup in cigar box guitars, and they are a favorite amongst people experimenting with electric drum triggers. These 41mm discs feature a brass plate and 3.93" (100mm) leads. Resonant Frequency 1KHz. Resonant Resistance 300 ohm max. Capacitance 70,000pF +/- 30%.