Befenybay 2PCS 5mm to 8mm Aluminium Plum Flexible Shaft Coupling D20 L25 Connector Flexible Coupler for 3D Printer CNC Machine and Servo Stepped Motor（5x8mm）

I used these on my 3D printer and they work great. Excellent quality

one bolt came jammed and the head was already cammed out, the second one didnt have the relief cut all the way through so tightening is impossible

Both of the ones I received were so tight, I doubt they would separate in the event of a nozzle crash. Ironically, the one I did use slipped on the motor side, causing a nozzle crash, despite being tightened to the point I was worried about stripping threads.

Works great used it to replace a damaged coupling on my ender 3v2, only issue I encountered was the screws not quite fastening the coupling to the Z motor properly, which was fixed by using the screws for the original coupling.

this coupler has one job: be straight. It isnt. Its off by at least 2-3 degrees, which takes considerable torque to overcome if your motor is mounted firmly. I think (think, not positive) the problem is in the rubber piece, not the aluminum. The rubber is tight fitting and allows no play, which would be good... if it were straight. I sanded the rubber ears down and introduced a bunch of slop so that my motor would quit stalling as it binds up every rotation. I used it for something that doesnt require any precision so it was good enough after I fixed it, but i would not recommend this for any kind of 3d printer or CNC.

The bottom of the clamping screw hole was foil thin. Couldnt figure out why it wouldnt clamp on the stepper shaft, got to looking a little harder and saw the bolt bottomed out on the other side of the slot.

I purchased a cheap flexible shaft coupling for a home made CNC machine and broke it within 2 weeks. I replaced with these more expensive coupling with a different design and these work great even when upgrading my motor from N23 to N34 size. Is still working 6 months later with no problems.

These are bored off center and wobble all over the place. There is noway they will work on a CNC printer. I would not purchase these at all.

These are most probably planned to separate, so these do not work for my use case: couplers for cartesian 3D printer z axis leadscrew. When moving z-axis, either one of these will separate. The grip is good, too good. Now I wasted two stepper motors because I cannot get these off without bending the axis.

Took me some time to figure out what was causing the banding on my print. When I took the lead screw out and looked at the shaft coupler while it spun, you can easily see the top piece wobble, thought it was just a bad z-screw initially, but after replacing that first, it had to be the coupler.