We see a lot of cars equipped with System 1 filters and we personally use them also. These filters thread on just like a normal screw on filter and they have a removable threaded cap on the bottom to service/replace the filter. Occasionally when we remove the filter for disassembly, we will find that the threaded cap is very tight to the body and hard to disassemble. We end up using strap wrenches or other tools that damage the finish and still don't always get the job done. This simple wrench locates in 2 holes of the filter and holds it in place while using a wrench on the cap to loosen.
