... balls have good surface,and precision.2)the ball is made by 304 stainless steel, and the holder is made by plastic ... .3) our products are sold to European and American area ... ,ABS,POM,PA,PMMATrackball,Ball valve,Bearing ball, Roll on ball,and so onHollow ball10mm-100mmPP,PE,HDPERoll on ball,Bearing ball,Ball valve,Floating ball,and so onRoll ...