These Faithfull Impact Screwdriver Bits have the following specification: Size: PZ2 x 25mm Pack Quantity: 20 Faithfull professional 1/4in Hex Drive Impact Screwdriver Bits are specifically designed for use in high torque impact drivers. Manufactured from a unique material that is engineered for extreme durability, these bits have an increased working life compared to standard screwdriver bits. Impact bits are designed to distribute impacts evenly, preventing energy waste for efficient screw driving. They incorporate torsion areas to absorb torque peaks and to reduce stress at the bit tip during heavy loading. All bits feature a precision-machined tip to provide an optimum fit, helping to prevent screw stripping and cam-out.