Its sound property is rather difficult to fulfill for other balls. Its properties are as follows: 1. High hardness, high abrasion-proof, high whole hardness: its surface hardness is HRC56-60. its central hardness is HRC54-59HRC. The hardness difference is less than 5HRC. 2. High tenacity: the impact tenacity is more than 17J/cm2. Extremely low breakage rate: the properties for peel resistant and breakage resistant is more than 100 times those of other products. There are almost no breakages when ball impact times reach 100,000 to 200,000. Actual breakage rate is less than 0.1%.