Remix of https://www.thingiverse.com/thing:3209211 , extended the thread so it would work on the stock cr6 arm. Use the roller and the nut from the original. I also added a version that twist locks into the factory arm. One is for inner mounting so the body of the roller is toward the front and one for outer mounting where the boday is toward the rear to allow flexibility in mounting, see pictures.. If you print an inner and then deside to go outer you can still use it but the body will not rest on the stop. Final note if you install this and its facing down , just reinstall 180 degrees.