These O2 sensor extension harnesses are sold in a pair of TWO.
They are used to relocate the front 02 Sensors (AFR) from the stock location to a new location like into the collector when long tube headers are installed. The URD Spec-U Equal Length Long Tube header as well as the JBA and Thorley brands carried by URD have two mounting locations for the front O2 sensors, upper in the center tube, or in the collector.