Ok, looks like it is a Xiamen Rizheng kit; the reason I say is because each component in the Rizheng assembly instruction sheet appears to be an exact match to the components found in the kits. There are absolutely no markings on the packaging, which, by the way looks like some of the older packaging from Smitty's Pen Works - long, narrow zip lock baggie.
As for the tubes, etc., I used only what came with the kit: 2 identical length 10mm brass tubes, the "center band" with the flange filed down. I did not use the 2 center band rings, and I may have made the entire pen too short by the thickness of the 2 rings (0.22")- BUT the pen extends and retracts just as it should (it fully retracts within the nib, thus not leaking in one's shirt pocket).
I will say the click mechanism works, but it appears to be, feel, and sound rather bush league. I hope I didn't pay too much for these kits. HaHa!