The Milwaukee Shockwave Impact Duty Magnetic Bit Tip Holders are engineered for extreme durability and up to 10 times life. Made from proprietary steel and heat treated to control hardness, the Shockwave Impact Duty Magnetic Bit Holders offer a magnet, which allows for a secure grip and bit engagement. The 2-pc construction of the holders also allows for abusive applications. These bit holders can be used with Milwaukee Shockwave Impact Duty Insert Magnetic Nut Drivers (1/4", 5/16", 3/8", 7/16" and 1/2").