This is a simplified version of Prusajr's PLA bushings. The geometry is nearly identical, but a parameter has been added to make the walls thicker/thinner, so that it can be printed with a different nozzle size without needing infill. The nominal contact area with the bar is also reduced slightly my making the tips that make contact flat instead of rounded.

It simplified because it is built in 2D and extruded, and uses less than half as many lines of code.