I knitted an apple green prototype pen tube for my Jinhao X750 (a fat black cigar with a B nib) as a prototype. Nice and soft, but thin. Also being crochet cotton it is always in danger of staining. Since January I have made three other prototypes in acrylic, two of which ended up like this:
and one of which turned out better knitted bottom-up. From now on I will make all my pen tubes that way. The more I do that method of casting on, the less complicated it gets. I suppose for someone who prefers to top-down socks one day I will actually be able to finish a bottom-up pair.
The attractive and spicy-looking crocheted gadget garment on the right of the green pen tube was made by Incredible Joie, for our shared Nikon Coolpix around first week of February. She used worsted weight Red Heart acrylic (must look for colorway in case someone asks later). Plus points: water doesn't seep in on an accidental spill, great cushioning, easy to find in deep dark bag.
I am trying to make a two-pen case. Some people of course might not think them presentable enough, but I actually use everything I have ever made, and if it works for my purposes, I will put them to good use.