This is the tiny string guide grommet used in RV Day / Night Shades. It prevents the string from fraying against the 3/16" holes drilled in the extruded aluminum rails.
The grommet on the left is the factory OEM version. The one on the right was printed in PLA.
Considering this thing is so small it can be challenging to get bed adhesion. But I did have success using a lot of glue stick, a 0.1mm first layer and 0.6mm layer height. I printed a skirt but did not use a raft or brim. Print speed was 20 mm/sec.
If you are restringing your shades you may also need my RV Day / Night Shade String Tensioner.
Check out my designs page to see other useful things I have made for my RV.