Our boat is new to us (2017 Mondo) so I'm not entirely sure if I have the pro tower but I can say that our tower is 2-3/8" (2.375") dia. I ordered a set of these and use one of them for the flag on the top bar above the bimini. The shaft of the flag fits perfectly through the hole in the bracket. I added a little stopper on the flag shaft so that it sits in the hole a couple of inches. Works great for us and looks much better, IMHO, than the purpose-built stuff on the market.
https://amzn.to/2CgCn30
boat pic for reference
Attachment 28772