That will not be autodimming at that price, autodimming is around £250 mark new and second hand are over £100 and very rare. I don't think dipping is related to glass at all, it's just a function in controller to turn it a bit down in reverse so that you can see kerb.
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Currently 8less
2011 Q7 S Line 3.0TDI, 2016 Tesla Model S 90D
8 history:
2006 A8 Sport 4.2TDI quattro SOLD,
1997 S8, reached end of life with gearbox failure
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