WARNING: This page is about a different car, the 2009 Mercedes-Benz E350 and 2008 Mercedes-Benz E350. However, it is still accessible from the selected car via links, so may be relevant.
FG 31/Set B
MODEL 211, 215, 221, 230
Use:
Unlocking tool for disassembling the trailer socket when repairing the cable bracket or when replacing the socket cover.