I purchased a used ultegra 6600 10 speed cassette. In the package I got this extra ring that I have no idea where it goes.



In this video he says that the ring goes on first but this ring doesn't fit on my hub. The gears fit fine. I put the cassette in and it seems fine without the ring. Any ideas?

https://www.youtube.com/watch?v=Xoq_xNYcYlA