I have installed them in three balls. Really like them a lot. Feel MUCH more confident with them, not worrying about them breaking. I broke a lot of Switch Grips. I like my thumb holes very tight, and feel the IT can take the wear and tear of my tight thumb holes.
Installing them in the ball is very easy for the driller. The hardest part is drilling the thumbs themselves, but even that is not hard. If you can find a shop doing them, I think you will be very happy.
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