The Outlet Thermistor, Black, specifically manufactured by Rheem with the part number RTG20006BB, is a crucial component used in Rheem tankless gas water heater systems. This thermistor is designed to measure the temperature of the outgoing hot water or fluid from the water heater unit. It plays a vital role in ensuring accurate temperature control and safety within the system. The black color typically denotes its specific function or compatibility within the Rheem tankless water heater lineup. As with other thermistors, it's engineered to withstand the conditions encountered in water heating applications and is housed in a protective casing to maintain its integrity.