Air-Ultrasonic-Ceramic-Transducers-Open-Type-Aluminium-Case-Prowave-400ST160-A-40k Hz-oslash-16mm-open-type-transducer-This-transmitter-consists-of-a-piezoelectric-disc-that-has-a-metal-resonator-bonded-at-the-centre-acting-as-a-piston-Prowave-400ST160-40 K Hz-Aluminium-Ultrasonic-transmitter-open-type