Wera's Bi Torsion Extra Hard bit range is specially designed for fastening into wood. The extra hardness combined with the softer Bi Torsion zone allows the bit to perform under the immense constant increase in torque applied when driving into wood. Allowing peak loads to be absorbed by the Bi Torsion zone avoiding premature bit breakage & enhancing the service life of the bits. The Bi Torsion system means that the bit has been precision hardened to allow the metal to flex slightly in controlled areas & absorb the stresses applied by a power tool. ideal to be used in general construction. Extremely hard wearing, premium quality. (Use the Wera Impaktor System for unbeatable performance in high voltage impact drivers).