This is a Z axis endstop support for a Prusa i3 kit from Voxel Factory (EiNSTeiN variant). I was tired to adjust the thing with a Ty-Rap. This will fit on a 6mm frame and 8mm rod.
Added more parts with Z offset of 1, 2, 3, 4 and 5mm from the stepper base. So choose the one you need/require and use it at your will.
See also my...
...endstop Y support: http://www.thingiverse.com/thing:82631
...endstop X support: http://www.thingiverse.com/thing:85368
The endstop support sits firmly on the stepper base and grip both the frame and the smooth rod.