Thanks, they are just things I've made in my spare time.
A couple I have made as presents for people.
Only a few have lids, they are not twist pens (you mean you twist twist them to expose the tip?).
Making lids for them is a pain as I like to line the inside of the cap with HDPE (plastic) to avoid scratching the pen. This means the cap is a much larger diameter than the pen and can look a bit silly.
The carbon fibre is bought in tubes from the internet quite cheaply and is fairly easy to cut / face the ends.
The titanium is quite a pain to machine, the deep 6mm bores are hard to drill with the titanium hardening or grabbing the drill bit and snapping it.
I plan to make one from carbon fibre / orange anodised aluminium when I get time.