Material: refined chrome steel (Gcr15 -AISI E52100) ,Accuracy: Standard Tolerance Class China GB/T307.1 P0 P6 P5 ISO 065ANSI ,ABEC-1 ABEC-3,ABEC-5 Low Vibration: three levels of V1, V2 & V3 Low Noise: four levels of Z1, Z2, Z3 & Z4 Clearance: four groups of C2, C0, C3 and C4