SunRobotics FLEXIBLE COUPLING 5 TO 5 MM-2Pcs(Silver)

These couplers are made of machined aluminum and have a spiral cut that makes them slightly flexible so they can be fit to two shafts even if they are not perfectly co-linear and will help reduce binding effects.The way they're cut, they're a little springy in the X Y & Z linear axis but not in the rotational axis. That means that you won't get increased backlash - so they're suitable for precision CNC work. This coupler will connect a 5mm diameter shaft to an 5mm diameter shaft.