This item is used in conjunction with the IntelligAIRE II refrigeration units. One end connects to your ThermoKing unit, the other end connects to a standard serial port found on PC-based machines. This cable is used with early model InteligAIRE II systems that have a meta 5-pin connector. You would still need the ThermoKing software to utilize this cable, which is not included. If you do not have a serial port on your PC, you also need part number 420575, which allows you to utilize a USB port.