Faced with a need to send documents rolled up in a tube, rather than folded flat, I sawed off a suitable length of cardboard tube from the heap, then discovered a distinct lack of end caps.
Well, once again, it’s 3D printing to the rescue:
The small ribs probably don’t actually do anything, but seemed like a nice touch.
They’re somewhat less boring from the bottom:
The fancy spider supports that big flat top and provides some crush resistance. The flat flange should collect the edge of the packing tape wrapped around the ends.
A firm shove installs them, so the size worked out perfectly:
Add a wrap of tape to each end, affix the USPS label, and they went out with the next day’s mail, PETG hair and all.
The OpenSCAD source code as a GitHub Gist: