... 1mm--60mm, mainly used in the industry of bearing.2) Plastic balls are made of different materials, such as PP, ... ball1mm-60mmPP,PE,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 on ... look forward to receiving your order! 5.5mm plastic bearing balls