When you install a set of BBK Performance long tube exhaust headers on your muscle car or truck the O2 sensors are relocated on the header that is no longer in the factory location and the factory O2 sensor connectors will not reach to connect any longer.. These extension harnesses are a must when Installing Full Length Headers - All 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) Locator Tabs Because factory connectors vary, some connectors may require the small directional location tabs to be removed from the ends of the connectors to click into place. The tabs can be easily cut or filed off.