1) shield / closure: open bearing, z, zz, rs, 2rs
2) snap ring: n, nr
3) tolerance codes: abec-1, abec-3, abec-5, abec-7
4) vibration level codes: blank, v4, v3, v2, v1
5) internal clearance codes: blank, c2, c3, c4, c5
6) noise level: emq v1 z2, emq v2 z3, emq v3 z4, emq v4