I have just measured some pipes which are similar, to the one in the thread these locking pipe and connectors are used on a lot of cars if not all cars and 9.9% of the time are the same size.
Just over 9mm
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So there is a chance that an 8mm to 10mm ID clear hose will fit the 12mm you have purchased maybe to large.
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The clear tube as clearly been stretched over the pipe already, note the diameter.
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These are the fitting below that have been measured.
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Hopefully it will help albeit a bit to late