When you install a set of BBK Performance long tube exhaust headers on your muscle car or truck the O2 sensor locations are relocated on the BBK header and mid pipe. The factory O2 sensor wire connectors will not be long enough to connect to the sensors any longer.. These extension harnesses extend the length needed and allow them to now connect easily - All our extension harnesses feature OEM Factory connectors to allow simple plug in installation to the factory wire harness so that the relocation is super simple and does not require any splicing of the factory harness at all. (Sold in Pairs)