This is a pack of premium 20mm piezoelectric diaphragm disc transducers designed for sound generation, vibration sensing, and acoustic pickup configurations [Image Context]. Each sensor consists of a circular brass substrate disc bonded with a high-sensitivity piezoelectric ceramic layer, pre-terminated with positive and negative wire leads [Image Context]. Operating on the direct piezoelectric effect, these discs function perfectly as acoustic guitar pickups, electronic drum triggers, vibration sensors for microcontrollers like Arduino, or ultra-thin buzzer elements.