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.

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.

Works well on Z-axis lead screw for my Ender 3, and is a definite upgrade to the stock coupler. The finish is decent, and seems pretty solid. My only complaint is that the coupler will come apart fairly easily if you apply any form of tension pulling on the coupler, which can get very annoying if youre used to pulling up on the X-axis gantry to manually raise it. Thats 100% a design shortcoming specific to my application, and not a fault from manufacturing.

Not much else to say other than these kept sticking on my dual z-axis Ender 3 Pro and causing terrible banding on prints. Woke up to a print I set overnight to see that one of them completely failed in the middle of the night and fell apart.

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

Needes for 10mm stepper shafts amd 1605 ball screws.

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.

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

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.

After 3 months of lite use, they completely separated. The rubber-type press fit seems to be dried out and has lost its flexibility.