Within the last few days I mounted an SA8 shifter to my R20. I first tried to snake it around the curves of a set of trekking bars, but that definitely did not work. Of course it worked fine as long as I mounted it on an open, straight section of bar. The clamp is metal but surrounded by plastic. BTW, I've had to carefully adjust the shifter cable to get it to work correctly. On my hub I must line up the yellow pointer with one of the red marks to get it to work. Yellow pointer to yellow center doesn't work at all.