Coil winding Ceramic wire guide pulleys (ceramic roller) is used on coil winding machine for enamel insulated wire or silk thread appropriate amount guiding, the china circle makes from precise ceramics, the surface smoothness that the china marks with a circle reaches Ra 0.2, moves up and down when rotating being smaller than 0.15 , material selects and uses 99%'s AL2O3 , hardness HRa 88, density 3.85.