The 4-Piece Hex Key Bits Set provides a variety of tool extensions for repair and assembly jobs around the home. There are three different groupings of hex bits, each on a separate unit. All components are made of heat-treated, chrome vanadium steel for durability and have comfort grip handles. There are a total of 25 hex bits, including a nine-piece SAE set, an eight-piece TORX set and an eight-piece metric folding hex set. It also comes with a bit set with six interchangeable bits.