I've made a few of them and they are not bad. The refills are not the best, but what kit's are? The bushings (sold separately) appear to be aluminum, so be careful when using them. I don't recall getting any printed instructions, but assembly is very straight forward. If memory serves me correctly, I do belive that this kit is built on an 8mm tube. Since the ends of each fitting is beaded, the final size of the turned barrel is forgiving; just get it in the ballpark and it will look fine. The cap is a snap cap, and is postable.
My only real complaint was with the construction of one of the caps. The caps are preassembled with the clip. The cap has the design on two opposite sides, and I had one cap where the clip was not centered properly. Although I didn't spend much time on it, I could not get the clip to rotate. YMMV
Although I like the looks of the kit and I think it's kind of cute, the finished pen just doesn't have the feel of a high-quality kit. The parts are chrome plated and the finished pen is very light. I would only be able to sell them for what they are: novelty pens.
Hope that helps, Mannie!