Felo PH3 x 25 Torsion Screwdriver Bit  Ideal for use with an impact driver or hammer drill. Standard screwdriver bits simply can not withstand the forces from these power tools leading to premature wearing and breakage.  Torsion screwdriver bits are specially designed with the triple ridge on the shaft to act as a shock absorber reducing the forces on the tip of the bit. Thus reducing breakage, increasing life and saving you money.