Part of wera39s unique bitorsion system using torsion technology this holder will dramatically extend the life of screwdriver bits the bitorsion system means that the holder has been precision hardened to allow the metal to flex slightly in controlled areas and absorb the stresses applied by a power tool it also features an auto bit lock for single hand bit change and a spin sleeve which allows the steadying of the screw start for an even longer service life use wera bitorsion screwdriver