Annoyed by frequently having to adjust your
Z-axis home position ?
I was too, but no longer.
Here is the Hall-O
The Hall-O is a non contact measuring device that reacts to magnetism.
Put it on your machine, put on the magnet, set the desired distance and your ready to go.
I am using 3 of these on the Cartesio, because I want all 3 reference positions to be exact, all the time, every time.
Detailed info can be found at RepRap.