carbide ball bearings: 1,ABEC-3,5;Z2V2,Z3V3 2,High speed 3,End cover:ZZ,RS 4,Noise level:Z1, ... .Features:1),Shield / closure: Open,Teflon Sealed,Rubber Seals,2 Metal Shield2),Tolerance codes: ABEC-1, ABEC-3, ABEC-5, ABEC ... :from 1mm to 100mm8),Outside Diameter:from 3mm to 300mm High Performance carbide ball bearings