These are the usual quality from Bosch. The drills have a very long service life and are meticulously crafted, every six run around! They penetrate easily into a concrete and stone, transporting well the drilling dust from the hole and leave clean holes. Even in brick they penetrate clean. Caution should be exercised when the drill hit steel, thereby turning their heads around quickly! Otherwise fully recommendable. It would be desirable have been if a 4mm drill would have been in the set.
