XB Clamp Flexible Coupling - 5mm to 8mm

These things rotate off kilter. Tried with old and new lead screws, and a new stepper - not sure if I got a bad one, but the default couplers rotate perfectly concentric compared to these.

Have all my lead screws on these now. Still allow some (very minor) movement to compensate for not-so-straight lead screws, but do a much better job at dealing with axial motion than the spring style. Particularly good if you use Z hop.

I've tried the spring-style and direct couplers. Had too much play on the springs and far too much binding on direct couplers. These allow for movement while mimizing the slop. They went a LONG way to reducing the z-wobble you see riding up the face of falt surfaces during printing.

These are much better than any of the rigid or flexible ones that I've tried.

Look at the title

I've swapped my original couplers on all my printers to these and they're nice to remove the horizontal hops you may get on z-moves. Not a huge difference, but nice little upgrades and after a few little things, they add up.