Easydeal 12pc 27mm Piezos with Leads-Cigar Box Guitar Pickups Drum Triggers Plate material: Brass Easy to install, easy to use Resonant frequency (kHz): 4.6 +/- 0.5 KHz Resonant impedance (ohms): 300 max Capacitance (nf): 20.0 +/- 30% (1 kHz)