Klein Tools designed a set of ProFlex Torsion Zone Impact Driver Bits for the professional tradesman and do-it-yourself enthusiasts. All of the bits are made of high-impact rated S2 steel and feature an optimized torsion zone that absorbs impact forces to increase the lifetime of the bit. The 3 in. bit holder and 1/4 in. and 5/16 in. nut drivers have strong magnets to easily hold bits and fasteners in place. Minimal chamfering on the nut drivers hex pockets increases surface contact between the nut and driver for better performance. All 40-pieces fit in a durable, impact-resistant case featuring steel hinges, a stay-shut latch and modular stackability with other cases of similar design.