Milled fibers are ground to 2 mills. long. They add a lot of strenth to a joint. I know, I had to cut my stab back out as it was off center by 3/16 in the TE. All I can figure is that I move it while centering it up with the nose center line. I was watching the forest but missed the tree type of thing. It is NOW dead on and triple-triple checked. It is embarrassing but I caught it before I moved onto the wing setup.