Review on 🔌 Befenybay 2PCS 5mm to 8mm Aluminium Plum Flexible Shaft Coupling D20 L25 Connector - Ideal for 3D Printers, CNC Machines, Servo Stepped Motors by Michael Glassburn

They work better than machined spring clutches because they handle misalignment better (when the shaft rotates and is slightly misaligned) and because they center the shaft better - fixing the Screwing will bind the coupling, not the shaft (usually the set screws will push the shaft slightly to one side or the other since they are in contact with the shaft itself - this can also create small indentations in the shaft where the set screws bite). not bad!