Black Allen keys are made from Chrome Vanadium Steel which withstand upto 30% higher torque as compared to Allen keys made Carbon Steel, Taparia Black Allen Keys are scientifically hardened to 52 to 56 HRC. Other makes Allen keys are usually offered with hardness in the range of 48 to 52 HRC. As a result of higher hardness offered in case of Taparia Black Allen keys along with superior steel properties the wear resistance and life is more of Taparia Allen keys. Allen keys are precision drawn for perfect matching of Allen keys with screw head.