The Thinline 332® Martin Acoustic Guitar Pickup is a piezo-ceramic under-the-saddle passive pickup system. Six electric crystals are imbedded in a piece of carbon graphite laminate to produce clear, dependable acoustic sound. Piezo (Piezoelectric) ceramic crystals emit an electric signal when pressed or vibrated. Using the Fishman Transducers technology to design the acoustic guitar “Thinline Series” pickups exclusively for C. F. Martin and Company.