Shield / closure: Open ball bearing, Z, ZZ, RS, 2RS, 2RZ 
Tolerance code: ABEC-1, ABEC-3, ABEC-5, ABEC-7 
Vibration level: V4, V3, V2, V1 
Radial play: C0, C2, C3, C4 
Material: AISI52100, AISI440C, AISI304, AISI316 
Retainer: PTFE, nylon, PEEK or (stainless)steel