... :EF-ZB02/ EF-ZB03 Material:Nylon,PU, Rubber, Super artificial rubber. Size:v2' -5inche Caster is important compoent of Wei Tao-line ... system,which commonly used in worktables, carts,racks.There is caster iron rubber wheel ,super artificial rubber wheel ,PPwheel,phenolicaldehyde wheel ... it. It's divide two style:With brake &Without brake PU switch caster for pipe rack(Shelf)