Features: Silicon nitride ceramic precision balls are high-temperature sintered in non-oxygenation atmosphere. They have many advantages which metal don\'\'t have, such as high strength, wearable, corrosion resistance, high-temperature resistance, non-magnetic and low specific gravity. Advantages: 1) Corrosion, acid and alkali resistance, it also can be used in seawater 2) High temperature resistance, its hardness is keep nearly steadily in 800°C 3) Non-magnetic and insulator, it can be used in magnetic field 4) Light weight, it is only 1/4 compare to steel, and the density is 3.20g/cm³ 5) High steel like, high hardness, its hardness is double than steel, and modulus of elasticity is also higher than steel 6) When high-speed rotation, the centrifugal force is small 7) It\'\'s coefficient of linear expansion is only 3.2 x 10-6K, nearly 1/4 of steel 8) Its self-lubrication prevent pollution from lubrication contamination efficiently 9) Resistant to medicine