IMHO they are the best! I have the sleeves in all of my balls and every thumb I own can go in any ball.I have, and use, 5 different thumb sizes.Before Tom's Thumb,my thumb would vary by as much as 12 pieces of white tape!Now,I just put the right thumb in and always have a perfect fit.Most pro shops don't yet carry them because you must install them correctly.I believe this will change with time.Someday,interchageable thumbs will be as common as finger inserts(especially since the thumb is even more important than the fingers!)
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the pooh