This works great. I had to make a lot of them, so I printed a 1.5cm diameter sphere a couple cm tall to help me press the bearings into the tubes when my thumbs got tired, but they fit just as snugly as you'd expect, are strong, and roll very nicely. After struggling with a few designs that were targeted specifically to Yoopai boxes that suffered poor fitment, it was nice to discover this great design that fits exactly right.

Printed these out to help with the assembly of a thing I'm working on, and I am so used to 3D printed mechanical parts being, well you know how they are, that I had low expectations, but this one actually works really nicely. The designer clearly understands the limitations of 3D printing, and I thought that the way the entire interior was a giant, gradual, softly threaded insert was pretty genius. The result here is that everything works really well. Assembly was trivial once I glanced at the instructions. Extremely well designed products here. 5 Stars.