Sludge and soap residue build-up on the sides of RV black and gray water tanks can lead to false readings. The patented design of Horst Miracle Probes prevents false readings because they 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. Black tank probes have a specially designed‚ over the probe sensor to prevent toilet paper from coming into contact with the probe and creating a false probe contact and related reading. Easy to install as they fit the 3/8" diameter holes of existing probes Compatible with existing wiring and monitors, so they can simply be connected to the new