• I have a couple of Shimano wheels with 11 speed cassettes.
    If I buy a bike with 9200 I want to be able to use them. I am not going to buy 12 speed cassettes when I have half a dozen 11 speed cassettes in the basement.
    If I break a 9200 rear derailleur I want to be able to put any di2 derailleur on as replacement. The exact replacement is not always available.

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