Tough aggressive and lightweight shimano slx m670 10 speed i spec b right hand shifter with vivid indexing and 2 way release function the shifting is light to the touch but positive and crisp vivid indexing provides a constant amount of shift lever force across all 10 sprockets adding to this the 2 way release where the upper lever still performs the same shift function but it can now swing in either direction allowing it to be released by the thumb or index finger the slx m670 shifter is