I was hoping for something that would let me mount 8mm lead screws without any compliance for very high tolerance. Solid mounts seemed like just the thing. The materials are good, and the machining tolerances seem reasonable, The grub screws tighten well enough not to allow any slipping. Centering the screws on the other hand is difficult and subject to issues. Be prepared to take a lot of time and effort to get your lead screws centered. You are very likely to see wobble artifacts in your 3D printer when using these couplers, unless you take care to use some anti-wobble measures at the nut part. I found that after some weeks of printing, that the scerws had developed some eccentricities in their centering. If the grub screws were in better relative positions, say at 90 degrees to each other rather than at 180 degrees, I believe that this would be better, or at least more consistent over time. They are nice looking pieces though, and I cannot fault the appearance or finish of the materials. They're also somewhat smaller than the typical flexible couplers, which is nice where you have limited space to get to them.