... steel ball , for 13 years in China, has earned trust from our customers in North America, Europe and Asia, ... 1 silk, absolutely guarantee the quality.2. Hardness: hardness in between 55 ~ 623. Imperfect rate: 100% through strict screening ... visual visible crack, defects such as corrosion, used in home and abroad quality casters, bicycle, force of ... etc. G500 soft carbon steel ball made in china