The Honda VTX1800 comes with an oxygen sensor in the O.E. pipe, for bikes built for the California market. Cobra pipes for the VTX do not use the oxygen sensor. An adapter that fits on the wiring to the sensor is available, which eliminates the need for the sensor. All VTX bikes in California must have this sensor eliminator if using Cobra VTX pipes. Also available for Kawasaki Vulcan 2000 models.