This is a simple idler pulley.

The base is mountable, featuring a 9mm diameter hole centered on the bottom. There is a 12mm clearance from the wheel to the bottom of the mount.

The wheel features a tight-fit cavity for a common 608ZZ bearing. The wheel is meant to be secured to the mount with an 8mm diameter rod that is ~48mm long. The rod is kept in place by the force of the load and the tight-fit of the hole. I am using a carbon fiber tubing, of ~1-2mm thickness with ~50 lbs of load with no signs of cracking and no slippage of the rod after ~1 year of use.

Be sure to print at least the bottom 1/3 with 100% infill. I had one break under ~50 lbs of weight at 30% infill with PETG. I have 3 of these mounted on a wall(1) and on a ceiling(2) suspending a kayak. I have put ~100 lbs of weight on them as a test with no signs of being over-burdened.

Always test the strength of your prints. Twice the weight of your intended load should be considered the minimum strength requirement.