The Irwin Impact Screwdriver Bits are specifically designed for use in high torque impact drivers. They are manufactured from heavy-duty, high-grade steel and have a 3 times increased life compared to standard screwdriver bits. Their precision tip geometry delivers superior fitment, reducing stripping and cam-out. The bits are Power Groove designed for compatibility with the IRWIN® Impact Performance Series™ magnetic screw-hold attachment. This set contains the following:1 x T10 screwdriver bit.2 x T15 screwdriver bits.2 x T20 screwdriver bits.2 x T25 screwdriver bits.1 x T30 screwdriver bit.1 x T40 screwdriver bit.1 x Bit holder. Supplied in a moulded ABS resin case.