This 12-piece set of flexi-head wrenches from US PRO is manufactured from Chrome Vanadium drop-forged steel, which has been hardened and tempered for enhanced strength. The spanners feature both flexible socket and open ends. The set includes sizes 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, and 19mm. The chrome vanadium construction ensures durability and the chrome finish provides resistance against corrosion. This set is supplied in a convenient storage pouch.