This litterally is nothing but a hemipherical top that sits on top of your hitchball are you lower your trailer ‘shoulder’ join down onto your ball.  Play with the three sizes provided and see which one works best; I think I went with the 3/16" hemispherical.

I have the silencing hardware that silences the hitch into the receiver for sure; but I have the trailer quick connect system that doesn't let you adjust the holding arm tension on the bottom of the ball once its locked into the trailer.  So how do you take up that extra slop of the ball banging around in side the cavity joint on your trailer?  Fill it with a plastic spacer!   Sure it will get mutilated by the time you get to where you're going…but it will be quiet the whole time!  Just print a handful of these and chuck them in your glove compartment.  Throw them out when they've been squashed to oblivion and replace!  

Easy fix, peace and quiet, cheaper than dirt, no time to print.