By default the M5 comes with 1m timing belt pre-assembled for ease of use. The upgrade kit comes with 2m belts.

Take careful note of the position of each belt in their connectors and match the fit for best performance (square drawings free of curvature).

If you have an older model disc, the hole will be larger than the Y clip. The disc has a rectangular hole. Make sure the long/wide side of the rectangle is touching the belt to ensure a snug fit. Try to center the hole on the hook.

If you have a newer model disc, the fit should only work one way.