small ball bearings:1,ABEC-3,5;Z2V2,Z3V3 2,High speed 3,End cover:ZZ,RS ... 4,Noise level:Z1,Z2 Z3 5,C2,C0,C3... Features:1),Shield / closure: Open,Teflon Sealed ... ,2 Metal Shield2),Tolerance codes: ABEC-1, ABEC-3, ABEC-5, ABEC-73),Vibration level codes: V4, V3, V2, V14),Internal ...