The E3D version was designed and tested to work with an E3D hotend or a Geeetech all-metal hotend.The J-Head version has been tested to work with a Genuine J-Head hotend.I use the z-probe temporarily for auto-calibration.You might want to use these with my carriage designs.If you need the ball studs, I had quite a few made, so I offer them for $1 each.I also precisely build carbon fiber arms to work with these.2016-02-15: Updated to add versions for J-Head hotends, add the z-probe, and tightened the part which secures the hotend.2016-03-28: Updated to add a version which works with the Ultibots K250 carriages (for use with 2020 extrusions).