Drilling and screwing without the need to change drill or bit at the bit lock. Simply turn the drill insert and tighten the screw in the object with the bit. The set consists of two high-quality 50 mm S2 steel bits, size PZ 2 and T 20, STANDARD, industrial quality, drive 1/4" hexagon according to ISO 1173, E 6.3, and two HSS drills with diamaters 4 mm and 5 mm with 1/4" hexagon shaft, for sufficient drilling depth to pre-drill roof battens and squared timber up to 40 mm.