TANK PROBE, GRAY WATER, C by Horst Dynamic Horst Miracle Probes are considerably longer than standard probes and the sensor is surrounded by a Delrin body and teflon tube which prevents any liquid residue or sludge from setting up a conductive path Easy to install as they fit the 3/8? diameter holes of existing probes Compatibility with existing wiring and monitors, so they can simply be connected to the new probes