... balls have good surface,and precision.2)the ball is made by 304 stainless steel, and the holder is made by plastic ... 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 on ball and holder8mm, 10mm,19.05mm, ...