U type groove pulley

These use standard 608 skate bearing and are rated for a lot of load. The bearing is not as frictionless as a fidget spinner, but it turns as easily as a skateboard or roller blade wheel does. I used these as support and guide rollers for a travelling rope system, like a scaled-down chairlift. I also looked at some larger diameter white pulleys, but those had a deeper grove with vertical sides, which prevents the rope hanger arm from passing through both vertical support pulleys and the horizontal main drive and idler wheels while keeping the same angle where the arm clamps on the rope.

Used for barn doors. Work great.

these exactly fit high pressure (heavy duty hydraulic) 1/2 inch pipe, which has thicker walls than ordinary water pipe, and slightly smaller diameter. A heavier bearing would be nice maybe.

Working well on a sliding closet door.

These nylon wheels are turning very smooth. Because they are wide and use single bearing, you will need 8mm spacers to distance them from the surface of attached material. Perfect for my project.

Very good little wheels. My drill press was slipping so I rigged this up.

The bearings are really low quality. They barely spin.

I was looking for rollers to guide a power cord on a lamp fixture that was to be raised and lowered. These units had a nice deep groove and were easy to design into a bracket. The bearings operate smoothly and the overall construction seems of good quality.