This is a small PTFE tube collar for passthrough tubing.
I have filament above one of my printers on a wood shelf, and directly feed the filament down into the printer from above.
I drilled a 4.5mm hole in the shelf which takes a PTFE tube easily. I then put the collar on a short length of PTFE tubing so that there is some relief at either side to bending.

A tiny bit of glue can be helpful to reduce movement if needed, but in my case it grips well, and gravity lets it sit in the hole.

If you wanted to be fancy, a collar at top and bottom could grip the shelving.

Print Settings

PLA filament is fine
This object is so small and takes so little loading that you could make it solid, but I simply used a single wall to allow a little flex when pushing the PTFE tubing through.