These Allen keys are for easily carrying out adjustments or repairs on your bike at home. This is a Set of 9 Allen keys in which a 5 mm adaptor for making the main adjustments on all types of bike. Black Allen keys are made from Chrome Vanadium Steel which withstands up to 30% higher torque. As a result of the higher hardness offered in the case of Black Allen keys along with superior steel properties, the wear resistance and life are more of Allen keys. Allen keys are precision drawn for perfect matching of Allen keys with the screw head.