The Irwin Tools 1840315 33-Piece Impact Series Fastener Drive Set is part of the new line of Fastener Drive bits designed for use in impact drivers. While most screw driving bits are simply compatible with impact drills and drivers, Irwin's Impact Performance Series fastener drive bits are engineered for maximum durability and long life with impact drivers. These bits are forged rather than milled, so they fit fasteners more precisely which reduces stripping and increases the life of the bit itself. Irwin's Impact Series bits have three times longer life than traditional bits. Manufactured with heavy duty, cold forged, high grade steel, they'll withstand extremely high torque output. Plus, a black oxide finish resists corrosion and increases the life of the bit. The 33-Piece set comes in an Impact Series Pro Set Case for organization and protection. This set includes a 2.25-Inch Magnetic Bit holder with c-ring, a 3/8-Inch Socket adapter, a 3-1/16-Inch Compact Magnetic Screw Guide, 3 nut setters, 6 2-Inch Power bits, including #2 Phillips, #2 Square Recess and T20, T25, and T30 Torn bits. This set also has 21 insert bits that include all three Phillips sizes, all 3 Square Recess sizes, T10, T15, T20, T25, T27, T30 and T40 Torn bits.