Welded 5-inch x9-inch oval muffler, 2.50-inch free flow perforated straight through core, wrapped with stainless steel mesh, double 24 round straight resonance. Limited lifetime warranty. In fact, the exhaust head section is the product of dealing with the era of environmental protection. In order to solve the problem of environmental protection, manufacturers should first reduce the pollution value of waste gas when starting the engine, so oil supply, ignition and air inlet should be coordinated. In order to control this accuracy, oxygen sensors must be set before and after the catalyst to monitor the air-fuel ratio; At the same time, a rear oxygen sensor is also needed to detect the change of residual oxygen and estimate whether to increase or decrease the oil supply and air intake according to the amount of oxygen consumed by the catalyst. Therefore, the three-dimensional head section is an important link in refitting the exhaust pipe..