Originally Posted by
DrMarkR
True for 8 and 9sp, but I'm pretty sure the 10sp shifters are different...
Shimano 105 5600-series shifters (10-speed with cables outside of bar tape) were double or triple compatible (whereas Ultegra and Dura Ace of the same generation, 6600 and 7800 series, were double or triple specific). For the 5700-series, 105 also went to separate double and triple specific LH shifters, and I believe that's also true for the current-generation Tiagra, 4600.