Special version of the HIWIN HG Profile rails. Instead of having holes for mounting from above, it has thread so it can be mounted from below. Which can be an advantage in some designs. Due to the mounting from below, its better resistant against dirt. Since the top surface is completely smooth. In the normal rails dirt can get in to the carriages if the bolt holes are not capped with the green caps provided.
Available from stock
Mounting from below, (thread inside the rails)
Cut always such that holes are equally spaced, and then deburred
Less chance of dirt entering the carriages, due to smooth surface