... 5,ABEC-7 4Noise level:Z1,Z2,Z3,Z4 Stainless steel miniature deep groove ball bearings1.Model:Open,Z,2Z,RS,2RS,RZ ... °C,as your requestRing MaterialRefined high carbon chrome bearing steel,Carbon Steel,Stainless Steel and Ceramic.Tolerance classGB/T307.1-94:PO P6 ... for relubrication and,there for,reduces maintenance costs.There are three types of such closed bearings:shielded bearings,contact sealed ...