Wera BTH BiTorsion Zone Bits.-Wera's BiTorsion Extra Hard bit range is specially designed for fastening into wood. -Hard wearing & long life due to the innovative BiTorsion system; unique precision hardening. -The extra hardness combined with the softer BiTorsion zone allows the bit to perform under immense constant increase in torque.-The BiTorsion precision hardened bit allows the metal to flex slightly in controlled areas and absorb the stresses applied by a power tool. -Extremely hard wearing, premium quality. (Use the Wera Impaktor System for unbeatable performance in high voltage impact drivers). -Use the Wera BiTorsion Bit Holder to increase the service life of the bit.-Ideal for use in general construction.