Shanghai Unite Technology Co., Ltd. is based in China and lists Ceramic ball------Si3N4 Ball on Global Trade Plaza. This product is an abrasive made of silicon nitride (Si3N4) ceramic balls, available in sizes from 0.4mm to 100mm and grades G3 to G40, with standard black color and optional gray upon request. The company notes stable quality and high consistency with ASTM F2094-03a standard for these Si3N4 balls, which are used in high-demand applications such as bearings and valve balls in aerospace, defense, chemical, medical, and electronic industries.