Hard and durable. Good oxidation resistance. Suitable for bicycles, motorcycles, automobiles, almost all types of electrical home appliances maintenance, etc. 10 Pcs Metric Allen Wrenches: 1.5 mm 2.0 mm 2.5 mm 3.0 mm 3.5 mm 4.0 mm 5.0 mm 6.0 mm 8.0 mm 10 mm