*Weld in O2 Sensor Bung* This is a must for all engines with a factory O2 Sensors IF YOU'RE NOT RUNNING YOUR FACTORY O2 SENSOR THEN YOU'RE LOOSING POWER Fits all Suzuki, Honda and Kawasaki O2 Sensors Yamaha part coming soon. Easy installation, Drill 5/8" hole and weld in bung We have other parts to make your engine swap and/or upgrade easier