Tarmac short VS long RD hanger 'lengths'

[robt57]

googling has not helped, anyone know the length difference
of the long VS short rear derailleur hangers??

#9890-4226 is the long, #9890-4225 for my SL3 S-Works Tarmac.

[rnhood]

I can't imagine it's a lot. If you are wanting to run an 11-34 on the rear, and don't want to put an XT or XTR derailleur on, then get the long. Frankly, I'd get the long anyway. It isn't going to make one bit of difference in shifting performance...if you are running Shimano.