I didn't find it was good to store my posca pens vertically with tip down, they had an habbit to leak a bit when I used them, so I started to store them horizontally, ie, laying around everywere on my desk.
Finally I made this to have them easilly accessible, and mount them under the shelf I have above my desk.
I added screwholes for 3mm screws, but ended up using doublesided 3m tape.
Not sure what sizes other pens are, but I have PC-1M and PC-3M.
The author marked this model as their own original creation.