Universal stainless steel weld-on o2 bung, could be welded to mild-steel, steel, and stainless steel piping. Great for custom oxygen sensor location, place it where you like to prolong the sensor life and get better accuracy reading. This weld on bung has a small step so you don't have to drill a large hole and it position the o2 sensor higher so that the sensor doesn't bottom out on the pipe (for small diameter piping- ex: Honda Ruckus, Honda Metropolitan piping size). Always great to have a spare o2 bung for your motorcycle, cars, hot rods, and scooter so that you could mount a wideband or air/fuel ratio gauge for monitoring and tuning.