These roller writers are great writing nibs , they lay down a nice fine wet line and write very smoothly but personally I will only use them in my kitless work . I think they look "Fugly" when used on the metal sections of kit pens . I bought some of them from Richard when he first introduced them and have made several pens with them and given them to friends to test for me and after about 6 months or so the only major complaints are that they are a PITA to clean out to use a different color ink . Some of the minor complaints are that they use a half of a cartridge to fill the chamber , one developed a leak at the vent hole and they do dry out if not capped tightly and are very difficult to clean if they do dry out , in fact one had to be scrapped because I couldn't get it to flow without skipping after cleaning out the dried ink .
As for the threading into the kit grips , I feel that close enough is not right for any pen I build , if it don't fit right I won't use it for that application , but that's just my sickness . I would advise that if you use these you should use the inner cap to seal the nib even in a screw cap pen . It is best to seal the nibs as tightly as possible to avoid the ink drying out in the section since they are so difficult to clean , IMHO .
Overall I will eventually be adding them to my line of pens on a regular basis .
