These irwin bit holders are suitable for impact screwdriver bits they are manufactured with heavy duty cold forged high grade steel to withstand high torque output from impact drivers they have a stainless steel body with a black oxide finished shank which resists corrosion and increases life the holders have a rare earth magnet that holds the fastener securely this magnet is four times more powerful than standard magnets the holders have a c ring design meaning that they have an external clip t