... and good quality 4,The materials are bearing steel Our bearing have high quality low noise & competitive ... , 16000, series.2) Materal used: GCr15,Carbon Steel, Stainless Steel, Chrome Steel,Bearing Steel3) Shield/closure: open bearing, Z, ZZ ... sewing machine, massage chairs, Textile machinery, Electric tools, Agriculture machinery, fitness equipment, etc. exporter v groove ball machine bearing 6403