EDIT: I'm an idiot, they are supposed to be put in different way... They work very well if placed with retainers horizontally instead of vertically.
I'm not sure should I complain about these, or the Millennium Steel Box Rack I have these in. These were recommended for the rack so I went for it. They do what they are supposed to, but they are a real pain in the *** to get into the rack. They don't go in too well, and once in, they slip out pretty easy. If you are placing one next to another, it's even harder to get them in. Worse is that if you have most of the rack assembled, but one of these end up popping out, you might need to do some unassembling to get it back in place.
All in all, your mileage may vary. They perform fine once in, but can take nerves and a while to get set up.