This is a simple, micro-switch based bed level probe that costs less than $1 to make and gets the job done, reliably. Is is semi-automatic, in the sense that you attach it to the extruder, run the calibration routine (G29 in Marlin or G32 in Repetier) and then remove the probe. That means it does not add any weight to the print head, a nice plus for Delta or Bowden based printers. As long as you don't bump the printer or change the bed plate, the re-calibration is not needed. It was designed to be quick-mount: it slides right on the effector plate on Kossel (8mm thick one) and it takes only a few seconds to mount on other plates that are 8mm or less. The jaw is adjustable and tightens for increased repeatability. In terms of height it should work for any hot-end that is less than 65mm in total height from wherever the probe attaches, which means both the j-head and the longer clones will fit just fine. In terms of accuracy: I get a 20 micron repeatability but I can't say how much of that is because of the printer vs the probe vs the switch, the bottom line is all of those combined are less than 20 microns which is more than sufficient for most prints. NOTE: If you are discouraged by manual probes and still waiting for that fully automatic sensor you might be surprised to how much of a difference this little thing can make: consider this will at least allow you to get the printer in a shape where it can actually print parts for a more complex probe. This should be lot more precise than the Kossel original allen key probe and more reliable than the newer FSR solution (at least for the time being) in the sense that it allows you to have a heated bed as well as a super-tight bed plate (safe removal of stubborn prints). The large version is compatible with both 1/2" (small) and 20mm (large) micro-switches. Additional parts needed: Note: Height maps generated with Repetier (Tools->Bed height map) and Excel.It was designed with the assumption of an uncalibrated printer so print however you can, none of the features are terribly important, the only surface that is important to be flat is the face that attaches to the bottom of the plate (the face that the screw tightens against). I am using mine with Repetier, I followed the instructions here: http://www.repetier.com/documentation/repetier-firmware/z-probing/ I connected my probe to the Aux-2 connector (GND and A9/D63) on RAMPS 1.4 and in the config I use the following (note some of the settings are overwritten by EEPROM):