I have these brackets since 2012, they do the job, just that it is expensive for two pieces of iron € 77 anyway!
Easy installation, no worries the above, sorry if the notice is not very technical or provided, but at this level it there's not much to add except that when you have an office with room (studio rta desk establishment) to the gear rack these elements become an obligation to save space and also to structure their environment properly.
See the photo below.
I first buy the preamp, then I hesitate to buy these brackets but it soon became a requirement for the reasons outlined above, it completed the contract ie a preamp that level and thus began rack some security, once you can go screw it will not move! Just a cheap but good hair when you love ...