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 bought two sets of these and both were bad. They are cheap so I did not go through the hassle of returning them again. I strongly recommend looking elsewhere. These are NOT the ones you should get. I struggled for days trying to figure out why the printer was failing, only to find out the problem was with the coupler. Bad on me for trusting a cheap product.

worked as it should and am well pleased

Good quality, much better than stock couplings.

One of them was straight but the other was completely out of round. These were purchased for the Z axis on my 3D printer and having any wobble was not acceptable.. I didn’t have to measure the runout to see how bad these were it was visible. They’re definitely not appropriate for a 3D printer.

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

Factory coupler that came with the 3d printer striped right out of the box. Ridiculous I had to order parts the day I bought it. Luckily this piece fits to spec. And I have a second one just in case.

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 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.

Sort of small

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