The Dometic Tank Monitor 4 (DTM4) has 22" probe, and these probes can be adjusted and trimmed to fit your tank Four tank level lights - Empty, Low, Mid and Full. International symbols for four tank levels. One level light always on. No electrical components come in contact with waste or water - no messy probes to clean! Easy to install on any fresh, grey or black water tank. Available with either 22-inch adjustable probes. Operates on 12- or 24-volt DC. Uses only 0.017 amps at 12-volts