These Faithfull S2 Grade Steel Screwdriver Bits have the following specification: Size: Hex 4 ;x 25mm. Pack Size: 3. These Faithfull Professional 1/4in Hex Drive Hex Screwdriver Bits are manufactured from high-strength, heat-treated S2 grade steel. Bits are shock and wear resistant and feature precision machined tips to provide an optimum fit, helping to prevent screw stripping and cam-out and provide a long working life.