The ball is screwed onto the winch hook before use. It prevents the winch hook from being pulled into the winch winding and simultaneously guides the cable when the ball is run over the guide rollers. My first winch lacked this ball, and with a faulty switch (always on), I pulled the hook into the winch. I didn’t notice this until the motor burned out and the winch was unusable except for the hook. The ball is printed in PLA with slightly thicker walls. It is for a 10mm cable, has a diameter of 54mm and fits M6 screws; on one side, 10mm nuts fit best – self-locking ones are recommended – and on the other side, M6 hex screws. However, its size can also be adjusted via the slicer.