Features and Benefits:?Use with Milwaukee SHOCKWAVE Impact Duty? Insert Bits?Proprietary steel and heat treat process for maximum strength and durability?Magnet holds fasteners to the drive guide?C-ring retains the insert bit?Custom alloy 76 steel maximizes resistance to wear and shock?For use with 1" insert style driver bitsMilwaukee? SHOCKWAVE? Impact Duty? magnetic bit holders are engineered for extreme durability and up to 30X life. Made from proprietary steel and heat treated to control hardness, the SHOCKWAVE? Impact Duty? magnetic bit holders feature a powerful magnet allowing for a secure grip and unyielding bit engagement. The 2-piece construction of the holders is the optimal assembly for abusive applications.