Vibrant Heat Sink Oxygen Sensor Weld Bung T304 SS (M18 x 1.5 Thread)Vibrant's Bosch LSU 4. 9 Heat Sink O2 Bung is designed to prevent premature oxygen sensor failure. The finned surface has been optimized to improve convective cooling, delivering up to 30% cooler O2 Sensor temperatures vs. a standard bung and the coped design makes welding easier.? This bung only fits a Bosch LSU 4. 9 Oxygen Sensor. Oxygen Sensor Weld Bung; M18 x 1. 5 Thread Size; 304 Stainless Steel; Fits Bosch LSU 4. 9 Heat Sink;