IRWIN Tools 1899939 Impact Performance Series Lobular Nutsetter Insert Bit, 1/2-Inch and  12-Inch Length Built for maximum durability and long life with impact drivers Lobular design drives fastener on side instead of corner for less stripping and longer life Rare earth magnets, with four times the hold of standard magnets, holds fasteners securely Black oxide finish resists corrosion and increases life of bit 1/4" quick-change shank is designed to work with impact drivers, and reduces slipping in standard drill chucks