When the two mountings for a loud speaker Attach one then of course, must accurately measure and drill so that the distance from each other best matches. But a few (few) mm can be compensated by the rotatable ball of the wall bracket.
With the result I am very satisfied. Although my speakers are quite heavy, hanging tightly to the wall and I see no Stabilitaetsprobleme. It probably helps that two supports were used per speaker ... As a result, the speaker can not "turn away" down (the lower bracket keeps the speaker from the wall), as would be possible with a single bracket. And easily to the left and swing right, the speaker can with the two holders also.
The only small criticism is that the screws are intended to be screwed directly into the box. There are installed in my boxing holders without thread, I had to get matching nuts. Since this many users but not sure need, I understand also that are included by default not.
Conclusion: If you have multiple attachment points per speaker, you can certainly bring severe speakers very stable on the wall with these brackets. Overall, I am very satisfied and the price is very cheap: 5 stars!