If you're trying to remove the upstream air/fuel ratio sensor from a Gen 2 Toyota Prius without removing the inverter then this is NOT particularly helpful. This does fit behind the heat shield on the sensor, however it's too long and in conjunction with a wrench or breaker bar it is nearly impossible to fit into the small slot available when the inverter is still in then engine bay. In the end I was able to get the part out, but it took me hours of trying to fit a huge crescent wrench around the end of it while slotted in a very small area. I think I was just super lucky that my air/fuel ratio sensor was not particularly tight and as I couldn't generate much force whatsoever.