White Paper on bearing tolerance and precision levels including definitions and specifications of ABEC and RBEC precision levels . ABEC 7, Class 4, P4.
(P4)，。 。 Large and precision spindle bearing(P4), with the best accuracy and rigidity. Powerful
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More specifically, bearings called Super Precision (MM) are typically manufactured to ABEC-7 (ISO-P4) tolerances. Ultra Precision (MMX) bearings are usually