Awfull. They where free for me so i dont complain, but they ran it way to fast. Somewhere there is 0.5-1mm difference between one side and another, which mean the edges and the holes are skewed. Just like if you drilled a hole at an 5 degree angle or angled your saw while sawing.
I had to make some bushings for the holes where the rails should have been and redrill them with both sides clamped to each other.
The edges doesnt really matter, but if you have them waterjet cut, skip the holes and drill them yourself