>>1138083that's a old suntour accushift shifter, i use them on my 90s rigid, they're my favorite shifters by far
they're like thumb levers, but they mount underneath the bars, next to the brake levers, and have indexing in back
but its not true indexing, more like indexed barends where you can move it between clicks a little bit
you can do super smooth shifts by pushing a hare past the click, then releasing it back into it
literally the best, smoothest shifting setup i have ever used, and its a low end 90s rigid that has been ridden hard for years
