Interesting demo, Jazz! Better than +-0.01mm repeatability, which is better than I would have expected. You look as if you are bringing the ballscrew towards the sensor from the side, and maybe it would be even better if you came at it end-on? But I guess we're starting to talk numbers which are down in the region of ballscrew and nut clearance, etc, and as you say in the video, it's certainly good enough for a router! I'll be looking to use something like this, now I've seen what it can do in practice.