In the drilling, the quality is super repays you have a smooth borehole what you indeed can not be expected in every drill, because you realize that these drills are not manufactured in the Far East but "Made in Germany" are. I personally have been a number of holes drilled in 8-and 10 concrete without any problems. I even once come to steel but if you notice it in time, nothing happens to the drill.
To Kunstoffkassette can say it appears to be high quality and fairly stable, but if it keeps really long will it take some time to not see already after 4 weeks ...