About this 3D model

Did this Remix of http://www.thingiverse.com/thing:355889 for own purposes. I have another system for holding my spool so I only needed a good and sturdy guide. Since I'm new to SCAD, STL and all that stuff, I do not know why my Slic3r loads this in a wrong size. I had to scale it down by a factor of .94 so it would fit my Simple Metal (and it's still a very close fit)