The length of the individual rails are shorter than the original and that affects the ability to make it straight. Ideally you want one stiff rail, that's easy to get straigth but that is hard to transport. So it's a compromise.
This works for shorter lengths like 1-3m but is not ideal for longer lenghts even if you can make that work too.
Quality seem to be good. Delivery also worked fine.
erland 
