This shimano deore t610 10 speed rapid fire shifters have a 2 way release which allows shifting from various riding positions the upper lever still performs the same shift function but it can now swing in either direction allowing it to be released by your thumb or your index finger the shift is light to the touch but positive and crisp while the vivid indexing provides a constant amount of shift lever force across all 10 sprockets the dyna sys10 speed compatible is perfect for use with prec