21508-02-12-05-02 is a Probe Proximity Vibration developed by Bently Nevada. It is a part of the Bently Nevada 7200 5mm / 8mm Series Proximity Transducer System. The Bently Nevada 7200 5mm / 8mm Series Proximity Transducer Systems are non-contacting, gap-to-voltage transducer systems that measure static and dynamic distances between the probe tip and the observed target.