I've bought two of those over the past year and they work well and stable in my DIY racks.
But I strongly advise to buy "real" sliding nuts, square and from steel, or use threaded strips. The hexagonal ones that come with the kit have quite the size distribution, and some so much slackness in the rail that they block every attempt to slide a module to make room for another one.
After all, sliding is the main reason I use, well, sliding nuts ;-)