12 micro bearing numbering system Callahan Bearing
P6: ISO class 6 (equivalent to ABEC 3). P5: ISO class 5 (equivalent to ABEC 5). P4: ISO class 4 (equivalent to ABEC 7). P2: ISO class 2 (equivalent to ABEC 9). P5A: ISO class 5A. P4A: ISO class 4A. PS5: NTN PS class 5. PS4: NTN PS class 4. PX1: Special tolerance. 7. PRELUBRICANT. 1K: Kyodo Yushi Multemp PS No. 2.
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