Yes, my goal is to make it possible for people to print pen tubes and use them directly with commercial pen kits, if only to bypass needing a drill press, lathe, or other costly tools and supplies. There might be a need to fine tune the internal hole diameter or total length using a round hand file or sandpaper but that's about it, as in this keychain pen example (HP black plastic): But pen makers have a very different mindset when it comes to making pens. A lot of them will look at a 3D printed pen tube with disdain. They only consider it a "hand made" pen if they go through the trouble of drilling and turning a chunk of something on a lathe. And pen makers will try to make a pen out of anything they can get a hold of that's large enough. Bone, exotic woods, acrylics, Bakelite, cactus skeletons encased in clear cast plastics, old toilet seats, old whiskey barrels, etc. I think there can be some middle ground to expand creativity. Things don't need to be black and white one way or the other!