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）

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.

The machining is horrible. I dont know if its made of aluminum or plastic.

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.

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

These will not tighten up on 5mm threaded rod. not enough clamping force. the cut should extend through the hole.

Such a simple upgrade elevated the z axis binding o had after upgrading to dual z axis motors

In my case the two shafts were not concentric causing horrible wobbles in my 3D printer. It’s possible the plastic insert was matched to the coupling pair. That’s not ok if you never take these apart. They are being returned.

After a few uses the coupler was stripped and kept coming off the z motor.

All good as expected

5mm was small. Had to drill it out a little bit.