My Railking Imperial Berkshire came with one of these in the box. I believe it was from the 2017 run.
The manual said it was only needed if you have elevation changes on your layout so I never used it.
It stops running from time to time so I would reconnect the drawbar connector and I'm good for a little while.
Now I realize I need to use this drawbar collar next time I run it and I should be good.
Brad