Before I say anything here I want to thank Randy for sending out this tip. I would not have known about the arm rest kit except that he mentioned it in this thread.
My arm rests came in today and I installed. They were an easy straight forward install. I got to drive around with them for a few minutes today to see how they work out for me. Here is my initial impression and review. I may update this later if I find any significant reason to do so.
I did not find the arm rests very useful for me. They do not come out far enough to provide any real resting place for my arms while driving or while operating my mower, which is the main purpose that I purchased them. This may have something to do with my size. At 6' 0", 245 lbs, I am probably a little bigger than most BX1860 owners. These arm rests may do more for someone of a more slender build than I am. Sometime in the next couple of weeks I'll ask my wife to test them out and see how she likes them.
One place where these may come in handy for me is when I am operating any 3 point implements that I turn around to watch working, such as my box blade or middle buster. I'll have a chance to test that theory in a few weeks when I box blade my driveway, and when I use the middle buster to dig holes for some trees that we will be planting.
Anyway, although these arm rests do not really seem that useful to me, I am glad that Randy gave the tip anyway. I think it is useful to know about parts from other model tractors are able to fit on mine.