1. Flat top can protect the studs from being destroyed by stress concentration. 2. Round edges can protect the stubs being damaged during production, transportation, installment and using. 3. HIP sintering ensure good compactness and high toughness for the products. 4. Special technology to eliminate the surface stress after surface grinding, and increase the surface hardness at the same time. 5. Grease used on surface of the products to avoid oxidization.