This spanner wrenched is used for adjusting and disassembling of Roto-Joints used in all UMI Performance control arms. Over time if the delrin race inside the Roto-Joint would wear, the spanner wrench is used to tighten the adjusting ring applying more pressure to the delrin inside. The spanner wrench is also used to disassemble the Roto-Joint for cleaning, inspection and rebuilding. For panhard bar Roto-Joints please see UMI Part # 0019.