0 or 5?

Usage: New with KS and Poroton stones. (Concrete / basement is Exposed as slots and drilling effort seems too high)
Alone when the function of the drill bit would be evaluated, I would have awarded 0 points. This occurs because the defective function of the screw to tighten the drill. As I read of this shortcoming but already in other reviews I was prepared for this and have therefore not surprised that the drill had dissolved after 2 holes. (In KS with whipped)
To me to save a continual tightening of the screw, then I have pre-drilled holes in the KS easy. The additional cost is certainly manageable. The drill bit required predrilled about 1min each hole in KS.
Tip from other reviews: screw replaced by a high-strength screw. How does this I can not judge affects time to the threads in the drill bit.

In poroton was without impact and without pre-drilling gearbeiter (drill the drill bit "loose") Here the pure drilling operation is much faster than in KS with the drill bit.
Conclusion:
after 60 holes in KS and 50 holes in Poroton the drilling time has slightly increased, without giving the feeling that there could soon be a problem when drilling.
The "loose" (only fixed minimla) drill makes both materials also no problems.
Wear after the previous use but not available to quantify exactly. (Regrinding with the corresponding grinding wheel certainly possible)
For the private sector to fully recommend.
Who sees but coming toward him through the screw problems he should not buy this drill bit.
(In concrete I'm reading different from here in other reviews, the drill bit is not used)