Piezoelectric Ceramic disc. Silver electrodes being one on each side (S configuration). Thickness mode vibration applicationPiezo Material: SM411Dimensions: 30mm diameter x 4.2mm thicknessResonant frequency fr: 500 KHz±5 KHz Electromechanical coupling coefficient Kp:=44%Resonant impedance Zm: =1.9 OStatic capacitance Cs: 2900pF±15%@1kHzTest Condition: 23±3 °C 40~70% R.H.fr, Zm, Kp => Thickness mode vibration applicationCs => LCR meter at 1KHz 1Vrms