Review on High-performance 3/8-inch Drive by 7/8-inch (22mm) Offset Oxygen Sensor Socket AP1822F: Chrome 🔧 Molybdenum Steel Construction with Wire Gate Access for Side Sensor Approach, Safeguarding Wire Integrity by Corey Holloway

O2 sensors are typically mounted on the top of the exhaust pipe so the socket is also on top. However, you and your wrench will end up under a pipe. If you try to attach the wrench extension (to the square hole in the socket) it will get in the way of the exhaust pipe. The square hole should continue to expand from the center.