Tolerance:ABEC-1 ABEC-3 ABEC-5 ABEC-7 Materials:AISI52100 AISI440C Carbon Steel Series Item NO. Bore Diameter(mm) 6700 673-678 3-8 6800 681-689 1-9 6900 691-699 1-9 6000 602-609 2-9 6200 623-629 3-9 6300 634-639 4-9 Inch R FR 1600 2.381-9.525(3/32"~3/8") Metric MR MFR 3-9 REMAKS:OPEN Z ZZ RS 2RS Teflon seals in available for all sizes