I'd been sitting on this really cool purple vintage cellulose material for a few years but had never used it, so I figured I'd try it out. The rods were only about 15mm, so I needed to downsize the pen to be able to make the cap from the material as well. It's a slim-ish pen, with cap threads of about 12mm and fills via internal piston mechanism that actuates when you turn the finial on the barrel. I made the hardware from silver and engraved the clip and cap band. The pen uses a jowo #6 nib.