That holds the whole back end together. The back rack & muffler bolts to it, then it bolts to the "D" Surrounding Spar frame. You don't want too much weight on it. Mine came loose & I tore it all apart to bolt it all together better.
Its a anti trailer hook up device. It stops you from hooking up a trailer when you have a 2" receiver hitch installed. It really sucks if you use your ATV for moving trailers or pulling a icehouse around!