Those are cheap junk. I suppose that if you got the them assembled, and they work, more power to you (pun intended).
As a professional master electrician, I can tell you that I would never specify that type of fixture on any project that we do. The only time I have ever had to deal with them is when the customer insists on supplying them.
Penny-wise and dollar foolish. It takes us so much more time to install these that in the end, the customer pays far more in increased labor costs, eating up any "savings" (and then some) that they think they had by purchasing the cheapest junk fixtures.