The Cal-Van Tools Oxygen Sensor Wrench, No. 843, features a flex head that offers essential clearance for removal and installation of oxygen sensors when positioned upward and inward to the floorboard, or when leverage is needed around an exhaust pipe. According to the company, it is designed for all oxygen sensors with 7/8" hex. It works on Ford Contours, 4.6L and 5.4L Ford modular engines, as well as 7/8" and 22mm knock sensors used on mid-sized trucks, SUVs and vans.