This is a grommet designed to fit the top surface of an IKEA Lack table. I'm mounting my spool outside of my Lack enclosure, and I wanted a nice hole for the filament to run through. Just drill through with a 1/2inch drill bit, and then this thing will pop right in. I used a little super glue to keep it in place.
This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/5l7V1x7DIAJ
Monoprice Maker Select 2.1
Building small tall parts like this will go much better if you are building something else at the same time.