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）

These have absolutely no pulling power, the plastic slides right out whether vertical or horizontal. Your z shaft must be secured on the end. They look cool though.

I can see where they have utility and where some people probably love them for certain applications, but I absolutely couldnt stand them at all. I bought a pair to use for an Ender 3 V2 printer when I was doing a dual-Z axis upgrade and just the littlest bit of pressure sent these couplers flying apart. For example, if you had even the slightest collision with your print bed, you were going to have to go in there and re-seat at least one coupler. And this is where I say I can see where they have utility for some people. I can see where that would seem like a perk to immediately limit the collision by disengaging from the drive train so you didnt smash your print head down into the print bed. But I found these would also separate during normal course of use causing inconsistent z-height adjustments on prints and horrible print quality. I went back to use the flexible aluminum couplers which are still fully connected but spiral cut in the center to allow for some margin of error in a collision, and flexibility for misaligned screw rods, but still fully connected with spring-back to ensure more consistent operation for long periods of time.

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.

The children wanted to extend the shaft of the motor and in turn, go from an 8mm to 6 mm shaft. This did the trick.

Der Kunststoff ist zu weich - und die Schraubenköpfe auch. Resultat: Man braucht viel Drehmoment um die Schrauben anzuziehen, damit die Kupplung nicht auseinander rutscht, und dabei macht man die Schraubenköpfe rund. Drei von vier gingen noch vom Schaft, eine nicht mehr und musste abgeschliffen werden. Für z.b. die Z-Achse an einem 3D Drucker wäre diese Schaftkupplung noch brauchbar, aber wer hat schon einen 8mm Schaft an einem Nema 17? Geht Retour.

Printer moves much smoother now after this upgrade, fits perfect with my ender 3, excellent quality

Sort of small

I like the quick delivery and i use it for my project.

To be fair I didnt try to adjust the cheap ones that came on the printer, or re-seat them in any way, but removing the original ones and installing these got rid of all the low pitch squeaking I got when rapidly adjusting the z health on my Cartesian printer.

hole was too large for my stepper. no matter how much I tightened it, it wouldnt lock down onto the stepper hex wrench eventually stripped from my trying to tighten