This harness is designed to connect between the oxygen sensor and the car's wiring harness.
 
The purpose of this harness is to allow a JB4 unit to be connected without modifying the stock connector. This is done using a plug-and-play method that doesn't require any cutting or the use of posi taps, which can leave a trace on the factory wiring.
 
The harness comes with a male and female spade that needs to be crimped into the JB4 blue wire. This helps to ensure a secure and reliable connection between the harness and the JB4 unit.
 
Overall, this harness provides a convenient and non-invasive way to connect a JB4 unit to a car's oxygen sensor without damaging or altering any of the factory wiring.