Originally Posted by libero

look at some images of each of them. I recall seeing a little gear indicator needle on one of these - tell what gear you're in without looking back at the sprocket. That could be of interest to some people. For all I know, they may all have this indicator. I do know that 105 and up (Ultegra, Dura Ace) do not have such an indicator. (But they are compatible with Flight Deck, whereas the 2300-Sora-Tiagra may not be.)