The plastic base with splines is kind of cheesy (BMW's fault, not the maker of the aftermarket clutch stop).
I installed a clutch stop on my E36 15 years ago. It was adjustable because the hole had threads and the clutch stop had a "stop nut", so you could adjust the height to your liking.
Still, I'll have to try one in my 135. Any other alternatives? I see
http://www.khoalty.com/bmw-pedals/cl...edal-stop.html, but not loving that one either...