Product review (5 stars): Fixed our leak and the handle rotates like new
We are on a well and have mildly hard water which slowly clogged the protective screens in our Grohe shower mechanism.  In the process of cleaning them out, some of the o-ring washers were damaged and replaced with after-market washers that were almost, but not quite, the right size.  They worked for a while, but were just barely too large, making it somewhat difficult to turn the handle to turn the shower on and off.  Eventually, I had to clean the screens, again, and the shower head dribbled after putting it back together.  I knew what the problem was, but I ordered the set of Grohe washers, this time, and they fit correctly.  Now we have no leak and I surprised myself, the first time I turned the shower on, after putting it back together because I was used to putting some muscle into turning the handle but now it turns so easily and smoothly.  Lesson learned:  Use the right parts.  I ordered an extra set of washers because we have 4 of these same shower systems in our house and I want to have one handy, just in case.