Sturdy and better than square Linear Motion Guides
I use this pair suspended holding my Z-axis for my CNC Machine and have no sag or bowing when cutting. It is very smooth in my setup and has very little twist. I found these better than using the rectangle Linear Guides using MGN bearings.
Super I wanted this items long ago for a projectSomething like a sliding table and they are perfectfor my table I_l will recommend this items to any home hobbyist. they are perfect for projects with a retractable or sliding mechanism.
jimbo "bones" 
