I originally designed this clip for my Jot Touch Stylus from Adonit. Since then, I have received numerous requests for clips in various sizes.
This clip is meant to be used with a writing implement 12.0mm in diameter. The collar is 8mm wide and 1mm in thickness. The stem is turned inward to give the clip more holding power.
I use this clip with two o-rings on either side and it has very good holding power. If you use this approach, I recommend going to a hardware store and buying o-rings that fit your stylus tightly. (For an example, please see the included photo.)
UPDATED: 11 JAN 2015