While most screwdriving bits are simply compatible with impact drills and drivers, IRWIN 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 Performance 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.Compact, portable design allows for easy transport to and from the worksite and ease-of-use while on the jobMolded ABS resin case holds up to rigors of daily useEasy-to-read size markings provide simple identification of set contentsConvenient bit holder storage compartment incorporated into top of case (insert bit cases only)SpecificationsItem #DescriptionContents186698310-Piece Impact Mixed Set1" Impact Insert Bits: PH1, PH2 (2), PH3, SQ1, SQ2 (2), SQ3, T25, Impact Magnetic Bit Holder with C-Ring 2-1/4"186698410-Piece Impact Phillips Set1" Impact Insert Bits: PH1 (2), PH2 (5), PH3 (2), Impact Magnetic Bit Holder with C-Ring 2-1/4"189992710-Piece Impact Square Set1" Impact Insert Bits: SQ1 (2), SQ2 (5), SQ3 (2), Impact Magnetic Bit Holder with C-Ring 2-1/4"189992910-Piece Impact Slotted Set1" Impact Insert Bits: 3-4, 4-5, 5-6, 6-8 (2), 8-10 (2), 10-12, 12-14, Impact Magnetic Bit Holder with C-Ring 2-1/4"189992610-Piece Impact TORX Set1" Impact Insert Bits: T10, T15, T20 (2), T25 (2), T27, T30, T40, Impact Magnetic Bit Holder with C-Ring 2-1/4"189992810-Piece Impact Tamper-Resistant TORX Set1" Impact Insert Bits: T10-TR, T15-TR, T20-TR (2), T25-TR (2), T27-TR, T30-TR, T40-TR, Impact Magnetic Bit Holder with C-Ring 2-1/4"189993140-Piece Impact Mixed Set1" Impact Insert Bits: PH1 (2), PH2 (5), PH3 (2), SQ1 (2), SQ2 (5), SQ3 (2), T10, T15