These are parts that were used to test the effect of widening the bearing hole in the Z-Upper to allow more lateral motion of the top of the drive rod in instances where the drive rod is bent, to reduce the appearance of Z-Wobble in prints.
Initial testing confirmed that this does effectively reduce the amount of Z-Wobble seen in prints depending on the severity of the bend in the drive rod. However, due to the extra lateral motion the drive rod would be capable of during shipping, it was decided not to implement this change as the probability of failing the shipping drop test would be greatly increased. It is not reccomended to ship a machine with the modified Z-Upper in place.