After not using the probe and then finally breaking down and getting one, I don’t see why I didn’t get it in the first place. No longer am I concerned with bit changes and how a carving will turn out. On the other hand, I have two x carved, I use a laser on the second one. I would love to have a manual z knob to turn when using different thicknesses of materials because the laser is set right at three inches from any surface and the program I am using only works in x and y planes. I can see the need for a manual knob for the z axis in that case.