A/3K-O-BB - NEMA 3R (Bell Box) rated enclosure with outside sensor probe.  Sensor Specs: 3K Ohms @ 77 Deg F (25 Deg C) Type II Thermistor

A/3K-O-EH - 3K Ohms @ 77 Deg F (25 Deg C) Thermistor The standard outside air configuration is based on an European style enclosure that locks out moisture with a gasketed cover and watertight fitting. They are designed to be mounted flush to an exterior wall.