I have it installed in four balls and have two of each size thumb insert from 61/64" to 1". That way when the thumb swells, just pop in a bigger insert in the strike and spare ball and it's happy times again.
To get the thumb slugs to fit right was the problem. I needed to file out the front edge at the tendon and open up the top all the way around so I could get my thumb deep enough into the ball but still have it fit the knuckle. It took a lot of slow careful work, because once it's gone you can't put it back. It took about a month to get it right but now this system is outstanding. I used to go through anywhere from 0 to 15 pieces of tape in the thumbhole each night with each ball I used. The tape irritated the thumb and it swelled faster if it wasn't put in right so it was a never ending battle. Winter to summer the thumbhole changes were huge so this system is the answer for me. The only drawback is it isn't cheap and you need some good proshop equipment to install it, as you have to grind off the excess sleeve and insert so it fits flush. I believe my system is made by Vise Grip. A drawback for the installer was the drill stop for the bigger sleeve drill didn't work well on a horizontal drilling machine.
