X-Ends-Prusa i3 8mm Threaded Nut

I created these X-Ends to be more accurate with Z. The 8mm Threaded rods will allow this, read more below. These Ends also accept LM8UU Linear bearings for the guide rods. Important: When loading these files into Repetier-Host, I get the message that they are not "Manifold" & may not produce expected results. [Slic3r still slices them] I created these with Sketchup & it says they are fine, as were my prints.

Why use 8mm threads?: ( I plagiarized this next paragraph) It's a very good idea to