1. Thermally wound shank for high abrasion resistance and longer lifespan 2. Internal tube (for flushing) of corrosion-proof and indestructible steel 3. Internal tube (for flushing) painted with special oil for corrosion and abrasion protection 4. Steel have two grades:Normal material 95CrMo and Super material 40SiMnCrNiMo 5. High precision, special bronze-brazing treatment.